This is sort of a revamped version of a previous post I made a couple years ago, since the game has changed a lot since then.
So, the rocket booster seems a little… dated design-wise to me. It looks out of place on a lot of vehicles, and I think it could use an update. What I propose is the addition of several other version of the booster that all look unique but offer no advantage or disadvantages, they solely exist for cosmetic reasons.
The main thing that differentiates them is the size, with each variant being available for a specific size of vehicle.
Lets start with the smallest: the JATO engine. JATO engines look similar to propane-canisters, and are used to help overloaded aircraft get off the ground during takeoff. JATOs are usually in groups but a single rocket can be used on the smallest vehicles like the Peel P-50 and the Go-Kart
The second variation I propose is a small jet engine strapped to the roof or bed of midsized vehicles like the Chevrolet Impala and the Ford F-150 Lightning. Most of these jet engines are taken from smaller private jets or helicopters, and I think their relatively small stature is perfect for most of the vehicles in game.
The third idea I propose is a fighter jet engine, perfect for larger vehicles like the School Bus and the Bank Truck. A fighter engine can already be seen on the Jet Truck in game, but would fit on other large vehicles as well.
For the very large vehicles like the Maus or Mountain Annihilator, I think it’s fitting to give them a very large engine, like the one used on the Space Shuttle. This one would need to be simplified the most I think because nobody in their right mind would ever model all those wires and pipes individually.
For the supersized vehicles added recently like the Ratte, a four-nozzle rocket engine would be fitting, this one coming from the first stage of a Russian rocket.
Of course, all of these would not provide any advantages to using it over the standard booster, but I feel like they would improve how most vehicles look with it.
TL/DR: Cosmetic variations for the rocket booster for different sizes of vehicles