Gotland wouldn't be quite the Oscar Wilde, but I would have thought operating them at around 18 - 20 knots they would be fairly efficient, not quite in lets say P&O's Norbay or Norbank's league, but reasonable enough.
I agree capacity might be a bit tight, with only 1 deck for lounges, restaurants, and a gift shop / cinema. But if ICG did a Stena Superfast style conversion, and were careful how they utilised the space, I say it could work. The current layout would definitely have to be revised. I agree the cabin capacity could be a bit of a problem, unless they attached an extra deck of cabins, just forward of the funnel, though this could effect the vessels deadweight.
Regarding Epsilon, she could be relocated to Rosslare, perhaps if additional capacity was required on the Pembroke run, or run a no frills service with the Visby or Gotland on the French run. Or option B, return her to her owners, though where this would leave Dublin - Cherbourg, I'm not sure.
Anyone any thought on Blue Star 1 & Blue Star 2? Built by Van der Giessen de Noord, famous for quality ferries, eg Isle of Inishmore, Isle of Inishfree, Norbank, Norbay, Mont St Michele...
Blue Star are also Greek, and have recently splashed out on small new builds (for another route), both ships were built in 2001, so still have plenty of life left in them. I understand they previously operated the Zeebrugge - Rosyth some years ago.