I don't care if Paris isn't direct (although of course I would prefer it to be), I'll still use it. I'm taking the kids to Disney and taking my parents-in-law to Paris as they've never been there before. I think it's great, just nip off for a weekend without all the hassle of getting to BFS.
I've haven't been in Paris for years but I'll definitely go this year.
In fact now that I remember I have previously flown from Derry to Paris with FlyBe. It was when they operated a feeder service via Belfast so it was Derry-Belfast-Birmingham-Paris-Birmingham-Belfast-Derry. So how's that? The price was right and the luggage was booked right through.
As for the other destinations, I'm not sure the Glasgow will do that great against a direct Ryanair Glasgow flight and it seems a bit odd to travel twice as far to get to Edinburgh but if the price is right and the journey time is less than travelling to Antrim or Belfast then why not? And Aberdeen and Inverness are more difficult to get to so why not avail of Derry indirectly.
Southampton (and Paris) don't seem as strange given that when you go first to Manchester at least you're heading in the right direction.