Most people do not like medic roleplay.
This is how it should work.
Give the medics a faction and some cars to make them happy. Those who want to participate in medic roleplay can, those who do not wish to participate, do not have to. A very small, small percentage of the playerbase actually enjoy medic roleplay. Most people don't enjoy it. Why would you want to roleplay with someone who isn't even enjoying it? They're just going to avoid, give bad responses etc. it won't even be enjoyable for you. So don't make it mandatory. This seems the most obvious way forward.