There isn't really a problem with large bonuses for the reason you mentioned, locked up Ether for a long period.
But there's a problem when only big investors can claim a bonus. That just means the rich will always have the upper hand and small investors have to pay a penalty for not being rich.
the big holders, rich, as you mentioned, are rich for a reason, are patient, hold their coins and face the difficult times with them, many small investors want to grow, but do not hold in moments that should support the currency out of fear, or for wanting quick wins