But they missed the BIG OBVIOUS solution: charge a pro-rated "first month" pledge, then combine all subsequent pledges like they do now.
For example, if I become a patron at the $10/month level, on the 15th of the month, they can charge me $5 immediately. Then the $10 gets added to my regular charge on the first of the month, and everyone saves in processing fees.
As a patron, I would much rather get one charge per month on the first. The current schedule works great.