I'm focusing on the important things: increasing conversion rate and getting customers through the site(SEO)
So here's my wanted list.
I think these mods are all achievable and would be very popular with most of the community, so there's scope to make some good money too. I'm not directly offering to pay someone a specific amount of cash to build a custom mod just for me - but suggesting some good mods which I think would sell really well - and some aren't too hard to implement.
Hopefully some of you dev's can "claim" a mod and do a good job, hopefully if I get some time I'll be doing a few too (although mine will probably be free contribs).
Newsletter Signup Only
...Removed.
...Found Qphoria's solution for this and bought it

http://www.unbannable.com/ocstore/newsletter
Built In Image Compression
Use a third party service such as SmushIt to compress images and decrease page load time. This is especially important as Google is putting extra emphasis on page-speeds in January.
Allow an option to "smush" all existing images for when adding the mod to an existing store, auto-smush images that are uploaded (e.g. via Product Image)
Price Range Mod
Simple version. A mod which can sit as a box on the site (align: left or right) displays a list of admin-created links which allow a user to view items by price.
So an admin can "Create option", adds a "From" amount and "To" amount, and then a "Label".
Example list:
"Cheap" (represents, From £0, to £10)
"Expensive" (could represent, From: £1000 to £5000)
"£500 - £750" (represents, From: £500, To: £750)
By allowing the user to specify a title/label for the range they can use names such as "Cheap" or "Expensive", or opt to display the actual value range.
The, just select all the items in that price range from the DB, simple.
This would be an amazing mod, since many people (especially at Christmas, although we're a bit late for that) only want to spend a set amount. Or they're just curious about what they can afford.
Example: http://www.ebuyer.com/store/Computer/cat/Desktop-PC
(look at the top-left of the left-side column where you can filter by price)
Page Caching - I don't have any experience with this, so it's a bit of a best-guess.
Again, a simple one which can have a massive payoff by reducing page loads times drastically.
Create a "pageCaches" table, each with the relevant page/item ID.
When a page/product is requested, rather than build up the page with all the DB requests (such as if a user is looking at a category of images with 12 products) - just see if there's any entry in the Cache table and throw it back out.
If there isn't, build the page as usual, save it in the Cache table and return the HTML.
Of course on Product/Page edit - update that pages cache.
I'm not sure exactly how OpenCart works with building a page up, whether it just 'Echos' the parts as it goes along, or builds up the HTML and Echo/Prints it at the end (which would be easier to work with, as you can just shove the HTML output in the DB).
Predictive Search
Google Suggest is out of the labs now and quite a show shopping sites use this as it not only helps avoid typo's (and hence a user can actually find what they want) but also helps 'suggest' products too.
Very simple, user starts typing into the Search box, AJAX query kicks in and looks up LIKE values in an indexed table.Table can be initially indexed and then on product update/add/edit it can be amended.
Abandoned Cart Reminders
Go to the GemsTV website, create an account, add a few items to your basket and wait a few days.
In 2 days it will email you to remind you that you've left products in your basket and that they cannot keep them in there for very long as they have "limited stock" and cannot "hold that price permanently".
In another 3 days time you get another reminder telling they're going to empty the items from your basket tomorrow.
This is a fantastic way of reminding a customer that:
A) They were interested in your products, and..
B) Hey, we're here! You were going to buy something from us, maybe you forgot?
Customer Variables in Mail
Simple concept, allow admins when sending out mail to apply a selection of variables like:
%Forename%, %LastPurchase"
If this is combined with "newsletter only" users, then you'll need to allow for "OR" values, such as:
[%Forename% || There]
would mean "insert the users Forename, or if the values not available, use the word 'There'.
Hence they could send out emails to all users, which are 'personal', such as:
Hi [%Forename% || There],
We hope you enjoyed your [%LastPurchase% || last purchase] and we hope to see you again soon...etc, etc,
Multiple CDN Usage
Again, Google are focusing on page speed, plus the faster your site is - the less likely a user is going to leave due to frustration!
Currently OpenCart supports an "images" location in the config file. Could someone make this into an Array?
Hence you can have multiple Image domains such as:
img1.mycart.com
img2.mycart.com
img3.mycart.com
and their server folder location counterparts too, so the site can save the images
wwwroot/mywebsite/images/img1
wwwroot/mywebsite/images/img2
wwwroot/mywebsite/images/img3
When creating images tags <img>, simply work through the list of image domains, so they get used evenly.
This means parallel downloads and a faster site

Each CDN domain option also needs an SSL option too. So basically replicating the current Config option to allow multiple image locations/domains.
Although, all features to upload images would also need amending to clone images to the Array of server image locations - so that all image files are available on all image subdomains.
Similarly, the same goes for creating a separate location for JS and CSS to help parallelise downloads.
Page Canonical Links
It seems that when using SEO URLs with OpenCart that a product can be found with various URLs, for example:
http://www.lovemoissanite.com/One-Carat ... eyword=1ct
and
http://www.lovemoissanite.com/Moissanit ... uster-Ring
Simply add the Canonical link to the page with the actual 'proper' URL, just to help the search engines along.
http://googlewebmastercentral.blogspot. ... nical.html
Fix SEO URL Mod
Similar to: http://forum.opencart.com/viewtopic.php?f=10&t=6677
Working...and packaged into a mod.
Product Filters
This is a big one - I know there are solutions similar to this "in parts", like the Tag Cloud mods, but nothing that achieves this....
Allow an admin to create an additional "option", such as "colour" which can be applied to multiple products.
(Currently opencart seems to request that you make a unique list of an Option choices per product...so rather than create a Size filter, and a selection of Options, then applying it to a Product...you need to re-create the options for every product separately.)
Allow products to have many of these attributes, so they can be filtered in many ways.
Use these attributes to create a Filter side-bar where all appropriate Attributes/Properties that apply to the current range of products are displayed in a list, such as:
"Colours:"
"Red"
"Green"
---------
"Size:"
"Small"
"Big"
"Huge"
Shoppers can then select a colour and filter their product view by this. They can also select other attributes to further filter their view of the products.
This is appearing on many sites now, from Ebay to Ebuyer - because it helps a customer find a product faster, and increases conversions.
So rather than trawling through a list of Sub-Pages and categories, such as:
Jewellery/Rings/SingleStone/RoundBrilliant
They can tick from a list of "Jewellery" - "Rings" to view all rings, then tick "Single Stone" from a list of Styles.
All the time, the customer always has a view of all products matching their options. They never loose sight of the products.
Example: http://www.ebuyer.com/search?page=1&sto ... subcat=354
(look at the left-side of the screen for product 'options)
Additionally, these extra attributes should be searchable, so if I tag an item with "colour: red" and "item: handbag" and someone searches for "red handbag" - the product will show up.
Also include the Price range as an Attribute too, so users can view products £100 to £400 (as mentioned before in a simpler version, above)