It's totally possible! In separate groups of 2 & 2! Hitching with 3 people is already hard enough. Imagine how much space 4 people is going to take up in a car. That's going to be one up front and a fully crammed back seat. You're hoping on what.. hippie busses? It's just absolutely not feasible. It can be done I guess but I'd imagine you're gonna take 8-10 times longer getting over the road waiting on that one special unicorn situation.
Where's all the gear gonna go? 4 packs in the trunk? Is the driver even allowed to have anything in their car before you guys all pile in? They'd have to have basically nothing in there and be really fuckin chill. Put yourself in the drivers shoes. Imagine picking up hitchhikers. One? Sure no problem. Two? Hmm, now I got someone in the back seat. Is he gonna slit my throat? I'm pretty defenseless with someone behind me. I'll have that one ride behind the passenger.. I guess that'll be alright. Three people? Now someone is behind me for sure! Like right the fuck behind me and I can't even see what they're doing. Now you wanna put another person back there?
It's an awful idea, but good luck!