You could have lava work like a kind of sludge that constantly does damage, but a no go area would be preferable.
I hope that units will pathfind their way around lava automatically, but if you're able to push enemy units into the lava, now that would be fun .
Spot on just what I would expect. So long as it's liquified and not solid but devs are already aware anyway they already know it's just the first iteration