As a menu it makes a lot more sense - showcasing all the things you could choose to have applied to your donor vehicle.
I think that there's also a market here for pre-researched, pre-tested modifications.
What I mean by that is that personally the R&D part is a very strong part of the attraction of a project - coming up with an outline, involving experts, sourcing parts, watching the slow gestation and eventually creation of whatever it is (currently, for me, engine and gearbox), then bolting it all into the car and seeing if you've made a terrible mistake.
This takes time, and money, and motivation - and the product may make you go straight back to the drawing board. I can see why allowing RPM to do all the work for a fixed fee would have a strong appeal. Same goes for the brakes, the chassis, the aesthetic/aerodynamic upgrades - you buy from them, you know it works.
It doesn't appeal to me, but I suspect there's a scale:
1. Buy a GT3, it all works, it's OEM and it has the best chance of giving you your money back when you sell it
2. RPM CSR, again it likely all works, it's built by a firm with a reputation and you may get back a reasonable % of what you spent
3. Buy a base car and tinker with it incessantly whilst driving various experts insane with ridiculous questions, eventually coming up with something incredibly expensive, incredibly personal, potentially a disaster, and with a resale value probably equivalent to the cars scrap value. But, ITB's.
I suspect that most people will read the EVO review, visit RPM and then have a few items off the menu represented by the car- a starter, a main course, second most affordable wine and a dessert, up to you lot what that list would be.
Gear-knob and handbrake, suspension, steering wheel and ducktail?
Anyway - it's a risk free route to a modified/customised/outlaw style car.
If you are money enough it would potentially make sense as the car that you park next to your GT3, if that makes sense?