Fun idea to float but
impossible, ok fine, very difficult, to implement properly.
The 8x8 board is 64 gems and a 12x12 is 144. We can round that to being double the size, and scale certain effects to match, but in general the balance would be a nightmare.
I mean, we have exploders generating 70% of the mana of gems they destroy that way, we can call it 35 or 40% on a double-sized board and call it a day. Right? No. Wrong.
^ That only works for the big ones like Gorgotha and Dragon Soul that blow up everything. We can’t use the same logic for something that explodes one gem, like Coral Golem, because that would take away a good chunk of its usefulness rather than balance it.
Just one of many examples.
“If there are 13+ blue gems” can be made 25 or 26+, easy enough.
Trolls “double then spawn some more” would be insane.
“Remove all purple gems” is okay actually, same effect as live. Destroy all, on the other hand, raises questions.