Building one Miniverse Playset made me think

Mattel could do something similar for TMNT.

They're like $20 and a bit bare bones... but modular.

Here it is with my Pizzaface Jr. I'm looking to get a second one to put  side to side and make a custom foam board roof... but we're not here to talk Miniverse... we're here to do Mattel TMNT. Picture something similar in true 6.5" scale. Hard plastic holey walls base and support structure for a top. Can we say Modular Sewer expansions, Channel 6 expansions, Technodrome rooms. These dioramas would be aimed for the adult collector, but making them compatible with kid core, is a great idea.

I need a second set so I can make it dirty manually.

They could copy some Jakks WWF elements such as this one that Figures Toy company has. 
 

Or if they wanna go beyond cheap that's what they could do cardboard with plastic frame and tons of accessories. Personally I prefer if they went plastic and modular.