Turrets do come as separate symbols. I took the "Ken" path with all chassis that go with them: if the turret has indeed gone missing I reckon some additional in-house drawing is going to be necessary. I might do a generic circular symbol for it, but sooting things up shouldn't be too complicated.

Too late: I am building a style around flat now! 😀

On a serious note, I genuinely like the paper theatre look - but it would need more consistency throughout, I think, and the tanks aren't cartoony enough for the part.