Be prepared to spend BIG, BIG money on a compressor, then. As in probably a couple grand to get reliable performance for the kind of sanding operations you're talking about doing. Even then the compressor will probably need some rest periods throughout the day which will mean downtime. Portable units usually are not designed for 100% duty cycle like stationary industrial grade ones are.
Is it really worth it to you to be spending a couple grand so you can run a $150 air tool, or does it make more sense at least initially to buy a $150 electric tool that is self sufficient and will sand all day long without complaining?