The barrier is if you still have feelings for him and at some level want to be back in a relationship with him.
We still had such a great bond between us, and that's what usually drew us to eachother, but we weren't taking into consideration that as a couple, we simply weren't compatible.
It is quite possible, but as long as you're open and honest with each other, and yourselves as to what your relationship now is. I tried staying friends with an ex for years who never totally got over his feelings for me and I finally had to give up the friendship. Yes, my ex and I are good friends, I still love him and he me. We had a big age difference, I am 14 years older than him and I couldn't live with that, so I left him, but he is a good man and was good to me so why not be friends, you will just have to let your sexual feelings for him go(if that's what you mean by strong feelings? You can love someone, really and truly but find its just not the kind of love that lasts a lifetime.
I have stayed friends with exhusband - on phone only - but I would say that any of my ex's if I saw them today we would be friends - never broke up on bad terms. I have plenty of girlfriends to keep me company and really don't want the complication in my life of x-boyfriends hanging around, nor do I want any shady x-girlfriends of the guy I happen to be dating in the picture either. So as long as you are on the same page it shouldn't be a problem. The barrier is if you still have feelings for him and at some level want to be back in a relationship with him.
I mean, there were other people in between, but it just seemed we couldn't walk away from each other.
It also ended up hurting me quite a lot over time, though.