Do not neglect the waiver process; in fact you
should push any things like this at the foundry
early on, to see what slack you can get.
You might be able to place, perfectly symmetrically,
density-improving features that will make the
foundry willing to waive "close, but not meeting"
densities. That's certainly more likely to happen if
gave it an honest try. Like, make your supply lines
"sandwiches" of metal layers and full of vias; put
poly "resistors" that go from vss to vss, or make
"decoupling caps" out of stacked active, poly, metal
and as many contacts and vias as can fit, again
place them so as to not bother symmetry. Use
more vias then you need. That kind of thing. Run
some density checks to see what you're coming
up...