Yeah, very much. Some basic dilligence with a somewhat even set of cells will probably be harmless. I would not be afraid of that kind of homebuilt power-store, if some decent practices are followed. (But you should do your dilligence & check to make sure all the cells remain ok, as you start using this pack!)

This... this is an hellish unbelievable nightmare, is asking for something to go wrong. It is certianly possible to invest the time & effort to balance the hell out of such a chaos-pack, but for one's own sanity, using normalized cells will save a lot of sanity & rework, and drastically decrease risks of catastrophic f-up. Don't do like this person! Do build weird electric systems though, unlike OP's way too broadscale doomsaying fear-mongering.