Oooh but there's multiple symmetries and I'd love if it fit 6x Iridium sprinklers with perfect coverage. And the
superbonus is that size and shape would be an odd number of tiles wide so would give the symmetry you're looking for as well.
It looks like it should be a way quick 'n easy map edit and I doubt there would be too many disappointed puppies out there. Ah! Even better, just another New Game checkbox:
[__] Symmetrical Greenhouse

Poke poke Mr. Ape