Good ideas... The Alpine I can see holding value as well. I've heard very good things. Only downside is it's a 4 cyl. Amazing curb weight around 1100kg. I'd say it's quite a different car to a Supra, M2, M4, Cayman.
Cayman is one of few cars I'd realistically move to from the Z, although I think running/parts costs would be far higher. Also the GTS with the 6 cyl is £65-80k...