"At least crash tests must be repeated because different engine types will destruct in different manner."
Probably not, type compliance for which destructive testing is specified would usually cover an entire vehicle model. Indeed this is not a coincidence, type compliance rules were written with an eye on what manufacturers considered to be one "model" of vehicle, and since then manufacturers obviously don't want to introduce a model which would consist of multiple types requiring separate compliance because of the added cost.
I haven't read the US rules, but the EU rules are clear that only a totally different type of power plant, e.g. batteries and an electric motor rather than a combustion engine, would count as a separate type and need fresh testing. So long as the body plan is the same, one vehicle can be tested as a stand-in for any number of variants in fuel technology, gearbox, etc.
Most of the crash testing we think of is actually voluntary, it isn't required by law as part of type compliance but is rather a consumer protection activity, albeit sometimes still funded by the government. NCAP and EuroNCAP for example, have no role in type compliance: vehicles that score badly in their tests aren't illegal, they can still be sold in the relevant countries and insured and driven. Car buyers do pay at least some attention though, which is why these programmers are still running. Like Europe's A-E letter efficiency grading on white goods, consumers show some interest in avoiding the poorest performers and that helps push manufacturers in the right direction without legislation.