The benefits of a higher sub are there already, no need to feel entitled to more because you add a few extra euro's to it. Under that pretext regular mogstation clients should also feel entitled to more or the ones who have more retainers as they provide more funds to SE as well.

Now, I do not think that a house should be limited to one account, I am thinking from an RP PoV now where every character is a different persona. One may opt to be a wanderer with no roof above his/her head but at the same time there are some who wish to be a restaurant owner with the appropriate interior while there are some persona who suit a cozy house more... and then there are of course the ones who prefer a castle!

Let the prestige of a house remain, open some new wards but let a house still be something that gives something special to an owner or FC. Rather introduce a way to prevent house snatching at the start, add an open auction of a week where gill is the only criteria to obtain one. Then add a system where you can trade house rights or have the option of a caretaker who can prevent the demolishing action when you plan to go on an extended holiday. (you can set a timer on the caretaker, hell I wouldn't even mind to see this appear in the mogstation)