I think it would be cool if we added pools to housing. For outdoor party where you can swim go down a slide. Fun floaty items and new inspiration for housing.
I think this would be best if we implement getting it though volleyball games and fun events where you get a new currency or golden saucer. This will prevent people that have billions of gil from just buying it. And make it fun to try and get it as a guild.
Volleyball game it would be fun to have volleyball to gain the pool. 2v2 or 3v3 volleyball where the more you play the more awards and glam you can get! making it a new fun game with the theme of obtaining your swimming pool!