I'd probably scratch off BWI-GSO. It's under 5-6 hours (and not too difficult drive) from GSO to the DC region.

I'm not sure Frontier would want to do BWI-MCO, but the market is huge. Anyways, I think for MCO and MDW, it's maybe more strategic to keep them at MDT rather than diluting off pax from MDT to BWI. I'm hoping for MDT-TPA, MDT-FLL and MDT-RSW this next winter, with the interest in MDT again with MDT-MDW for this summer.