Looks like the Sugino OX901D Compact Plus+ crank allows a 30 inner chainring, but they are fairly expensive. That would get the drivetrain down to 25 gear inches using the 32 cog. Not a huge improvement. Could get as low as 19 gear inches with a 42 cog, but an entire drivetrain replacement (other than FD) would run $600. Ouch!