Thank you all for the suggestions!
I think we'll go for the FS just to finally stay there because the rates are so good, and then if we're happy we'll return when the pool is operative again.
But I definitely want to stay somewhere else for the second night. I have made some more research (
this post was very useful, though the photos don't work anymore):
Properties that are open in March:
Lily of the Valley: near St. Tropez, modern, outdoor pool, seaviews, focus on spa, boutique
Royal Riviera: modern, heated pool, less luxurious, 50min massage for 2 via Amex FHR
Château Eza: dark rooms, old style, not much around, nice views
Château de la Chèvre d'Or: traditional luxury, Eze, high up, nice views
La Reserve de Beaulieu: traditional luxury, outdoor pool (looks similar to FS Cap Ferrat)
Hotel du Castellet: contemporary style, not quite as luxurious, up in the mountains, quite far away (Northwest of Toulon)
Hotel Martinez Cannes: I would earn a Hyatt night, modern, renovated, in Cannes (so probably more to do)
Properties that are still closed:
Cap Estel: traditional luxury, outdoor pool, ocean front property
Le Saint Paul: in the mountains, boutique, traditional luxury
Hotel du Cap-Eden-Roc: traditional luxury, ocean front property
La Réserve Ramatuelle: near St. Tropez, modern style, seaviews, but not on the beach
Château Saint-Martin: in the mountains
Le Mas de Pierre: Closed for renovation, will reopen under a new name
Of those hotels, I think that Chèvre d'Or and Lily of the Valley look best. Maybe also La Reserve de Beaulieu (people seem to love it, but it doesn't look that great in the photos?).
Which would you pick?
I guess it would probably make the most sense to stay somewhat in the area - so probably Chèvre d'Or or La Reserve de Beaulieu would be the best choice.