multiple sub categories to parent category

im doing a party orientated websiteat the moment using opencart 1.5.3
at the moment you have a catefgory tree such as

party > girls party themes > disney themes > disney princess summer palace
and
party> fairy and princess themes> disney princess summer palace

at the moment you need to create 4 cateogires for this to happen

would it not be better just to be able to assign multiple sub categires to parent categories as you can assign products to multiple categories

so fo instance you can create the category "disney princess summer palace" just the once and assign it to as many parent categories as you like