How is using a feature "abusing" it?
If PD didn't want every car to have a V8 or V10, they could have just, you know, not allow a V8 or V10 in every car.
You could say the same about car upgrades in general. Does the upgrade system mean nobody drive cars stock? I don't see how changing the engine is any different, it's an upgrade like any other in real life. It should simply be more expensive than any other, so you really have to decide if it's worth it.
Engine swaps in real life are rare because they're a) very hard work b) expensive and C) not particularly useful unless you're a serious enthusiast.
This is a game, for fun, where we can realise our wildest dreams not possible in real life. Or at least it should be.