Creating a FOSS EV is all do-able right now with off the shelf motors and batteries. Welding a frame would take some skill. How to title it would depend on the local government rules; many states in the US have a kit car designation for this sort of thing, but not all do.

If it's built rigid like a race car with a roll cage, four-point harness, and at least a DOT rated helmet for everyone inside (if not Snell), it could be safer then most cars on the road. If it's not very large, then it's probably safer for pedestrians and bicycles, too.

I don't expect air bags to be viable. It takes a lot of tuning to get them right, and they can be worse than nothing if not done right (they're basically a controlled explosion). However, the race car-like design above, plus helmets, would keep you safer than any air bag. Road cars converted to track cars often disable or remove the air bags. The rules of the event may even require it. They're counterproductive dead weight when you're packed in this way.

Other creature comforts are going to be what you put into it, but keep in mind that many of the things we take for granted in modern cars--A/C, stereos, padded seats, etc.--add a whole lot of weight.

What also adds weight is how many passengers you want to carry at once. Two passengers won't add much weight, but four or more would. All that extra frame material adds up.

Building a traditional frame would take some welding skills. I have just enough welding skills to make some shelves, but anything structural (which my tutor defined as "anything where somebody's life depends on the weld holding") is not something I'm comfortable doing. That is to say, it'll take more than a quick tutorial and a little practice.

However, one interesting possibility is epoxy. Lotus did this for the Elise, and I once tracked down the epoxy manufacturer they use (I'd have to search around to find it again, though). The instructions for it didn't seem to need anything particularly out of reach for a hobbyist (doesn't need a big autoclave or anything like that). Lotus did reinforce certain sections with bolts/rivets. It will take some knowledge to design a frame around this, but it's one time design work by an engineer and then everyone can copy it.

One advantage Lotus had over a welded frame was thinner material. A weld itself is very strong, but it weakens the metal around it (meaning you usually get breaks around the weld, not on it). You have to use thicker metal to compensate for that. Since Lotus was using an epoxy, they could use thinner material for less weight, and it was stronger in the end.

Since it's also getting rid of a whole lot of weight around the frame, the range you get out of those batteries could be extreme. It could also be extremely quick with a modest motor.

This is basically all to say that you can have any three: safe, creature comforts, enough space for passengers, range.