They'd look better as single piece walls and as you said, it would make assembly easier. To be honest, while I like being able to put figures inside buildings, I don't remember any occasion where I'd be bothered about which floor they were on. I'd just get irritated if I had to keep taking them on and off. I think having the split at roof level would be fine.
All that said, I really like them and would like a set of molds
Only question would be; have you got a step for "2 up, 2 down" front doors? The doors start quite a way off the floor.
Also, you want to trade a couple of the Forge World buildings for a full set of molds....

.... you've already bought a coaching inn....... you need to trade..
