I think Flybe did, to a degree, have a similar strategy to Porter with their operations out of City airport, where did they quite well.
They were obviously a much larger airline than Porter. Their problem was a lot of their trunk routes elsewhere didn't make much money. And if they did they were always in danger of a easyJet or Ryanair coming along, with a much lower cost base, and stealing their market.
With the right fleet selection, and free or ridiculous lease agreements, there probably is a bit of money to be made replicating a bit of Flybe's old route network. It's just never going to be a huge money spinner IMO.