I think the idea that you quick design a bunch of vehicles then delete the entire Design Studio(s) is not good. It is just a temporary placement that takes away the need for puzzle fitting as much as possible into the floor space available.
I have 2 ideas to rectify this.
#1 - If you delete the Design Studio, you no longer get to produce the vehicles it made. You’re back to just the Sedan. You can add a warning when you go to delete saying “if you delete your last design studio you cannot produce advanced body types”
#2 - To make the game more challenging, we need to place an additional Design Studios to produce more advanced body types like the open top sports car and off-road vehicle or some other combination. Right now there is no fight for space in the office factory floor. We need to make this a place where challenging decisions need to be made. And the same rules apply as above. If you delete the second design studio you lose the ability to make the open top and off-road body types.
#3 - As was mentioned in the suggestions thread viewtopic.php?f=54&t=19313 , there could be a degradation of design so you need to keep the design studio to keep things refreshed. But I kind of like the idea #1 plus #2 a bit more as it’s more black and white.
Here’s a pic to show how I’d suggest the additional design studio be presented (note I just randomly chose two. It might be better to have “pickup and off-road” or “off-road and the entire sports car set” for the 2nd design studio)