im surprised a company hasnt come out with a 'create your own RDA' type of business type deal. You could like pick what kind of deck you want (2/3/4 post, block posts/circle posts, shallow well deep well) from say a given amount of choices, chose what type of topcap you want, what kind of air holes you want in that topcap, what kind of driptip/widebore or not ontop. Like some generic kind of RDA styling thats just a deck and a topcap, but customizeability when you order.
you could like mix and match your topcaps onto the deck because they would all fit eachother.
something like this would be awesome and make a killing imo. Probably wouldnt be cheap, but I bet there are people out there willing to pay top coin for something customized exactly to their liking.