Not a problem, particularly when the promo appears to apply to pre-orders too, but unfortunately, it's not as simple as it appears
Lets say you got an attack off with Celestine and you cast a Chaplain's Blessing (not something Id ever recommend doing, but just for the sake of this example)
There's enough ways to deal with it before and after that mana generation, though, as you can interact while the First Day of Class is being used, or stop Makeshift Munitions from achieving its kill condition
If you dont want to play Crush Contraband over Return to Dust (even though the latter is ostensibly a sorcery speed effect) then consider spending that mana on something better
The set also seems to lack an issue like Streets of New Capenna had where one color White was so much better than the others and that at least one archtype was nearly unplayable at times (red/green)
GW Midrange / Counters Ive dragged on GW quite a bit, so you might be surprised to see it so high