I've said this before in other threads, so as to not beat a dead horse, support.
Pebble sinks in general are desperately needed to keep the currency useful and player engagement here. I'm fine even having the option to still pay for expansions in MS as long as it *stays* an option, not an expectation to continue playing. Ie, I'm not in favor of paywalling games, ever.
I don't think core gameplay aspects should be monetized, but if people wish to support dev or pay to avoid the grind, it's a good option to consider, but in general, this is a game with far too many MS sinks and hardly any non-premium currency sinks.