I was thinking it might be nice to have an option to buy two different kinds of dens with pebbles. The moonstone dens would still be there, but you could also buy a selling den and a nursery.
If there’s room in these dens, then wolves on the market automatically go in your selling den, and new babies automatically go into the nursery.
The user wouldn’t be able to use the dens for any other storage, justifying the pebble cost.
i also think it adds some utility and organization. Hopefully it makes sense

Hmm I think that it should be 2 minimum. Considering each den is maxed out at 50 spaces, buying extra dens is equal to buying extra slots (you get 10 for ‘free’ and the option to buy 40 more). There is a big advantage to having more wolves, so while i don't mind having some dens cost moonstones, I think more like at least half of the dens available should be purchasable with pebbles.

Or do it like FR where the amount of spaces is account-bound and you can distribute them among the dens however you wish, so that dens become more of a visual/organisational thing. In that case having just 2 pebble dens would be fine with me.

I support this. I also prefer having account-bound slots that can be divided into dens any which way. If I want a tab to only have two wolves in it, for example, i'd be wasting a lot of slots.

Support. I would also like for slots to be account bound rather than den bound.