And as much as I want it to happen, I won't be surprised if the "1 reroll ticket every month" part would get rejected, but I think 1 Master Ball per month should be fine.
Instead of a reroll ticket per month, I think it would be more balanced if it's 1 "reroll ticket piece" per month, and you need to collect 6 or 7 pieces to make a reroll ticket via an NPC.
Obviously, the pieces shouldn't be tradable.
Starlight's post in Daily/weekly/Monthly Login reawards. was marked as the answer