Safe cosleeping before we are ready for bed
Okay, judge if you want... but I just put my kid in our bed when he was that age. I'd sort of put a pillow or two around him so that he'd encounter blockage if he rolled too far. We never had a problem. I worried about him when he started crawling, but then my husband taught him how to get in and out of bed by himself, so when he woke up he'd just sort of crawl out of bed and come find us.
OP I had more or less the same issue, DD won't sleep anywhere but in our bed. When I put her to sleep in "her room" on a crib mattress on the floor, she won't sleep long at all. I put my mattress on the floor about that time. It's pretty thick too, and you could put some pillows to catch the LO if he rolls off, but my DD never rolls off. The issue is when they wake up and try to get off the bed. My DD would just cry for us to come get her until she learned how to get down (we coached her through it until she got it). I would just lay the little one down where he sleeps (by the wall) and maybe put some pillows where you've seen him attempt to get down, and then sneak in quietly when you're ready to sleep too!
I'm not here to judge anyone, but just to relate my experience. I was co-sleeping with my son when we were away from home, and he rolled off the bed, hit his head, and we had to stay a night in the PICU because they saw a small hemorrhage in his brain in the ER. Everything turned out okay for him, but we learned our lesson not to mess around with safety when sleeping. I had pillows next to him (instead of the bed rail we used at home) and he still managed to fall. It's really really scary, and I wouldn't want you to be in my situation. Ever.
OP, I would see if you can transition baby to going to sleep in his own room in a crib (or on a mattress on the floor, if the room is childproofed), and then just bring him in bed with you when he wakes the first time (after you've gone to bed). This is what we do with our son now, and it works pretty well, as far as giving some balance to the night's time.