I was at PIK not long ago too and took a wee walk around. It was totally dead, yet full of staff, 3 FR planes parked up and one departure on the board...for the next morning. It reminded me of the late 1990s when we used to visit the caravan park next to the airport and we'd wait all day and see about 4 planes land, all cargo or charters.
If it's at the stage where even Ryanair don't see the airport as viable then it really has to be asked if it's at all worth keeping open. Now that they are basically operating a handful of flights a week, which in time will no doubt move to GLA too, then it all seems a bit too hopeful that things will turn around for PIK.
It's only real useful role and only point for keeping the terminal going in a post-Ryanair scenario would be for diverts. It has the apron space and runway length to accept pretty much anything, and with a huge empty terminal it would be easy to accommodate passengers temporarily without causing any issues for other services.