Even though it reads nice, you have to understand that ZOS would not make any money out of this. Right now they can sell mount scrolls, with a skill line like that, nobody would buy them anymore.
So, it's unlikely to happen.

To be honest this is not where they should be focusing their income /business model. That should be done around creating the support for guild-housing, and improving the existing housing (by having more people space, and more premium items on the itemshop).

One good way to do this would be to create a lot more particle type effects, like water, fog, etc. stuff that is not based on the gif/png related material like that in housing tools addon, but more like the existing particle effects in the market/itemshop. Another great thing along these lines is some sort of system to allow players to place doors, that lead them to targeted area's as a house item, especially one that is premium.

Additionally, the introduction housing sizes, and the existing housing sizes really need to be re-evaluated, and more zones, especially those like cold-harbor housing (open, with out buildings) should be in effect.

working money off the mount system is a thing of old and really should be shifted out of the game for the betterment of it.

On the topic of housing, it would be really interesting to incorporate them in open world, or having guild housing some how put on display the individual houses. A massive guild zone with each persons houses in there would be interesting.

Imagine if that zone has plots on it, and housing build there was open to the guild, all houses the same, but maybe having houses have upgrade levels to expand their sizes (probably in a vertical way). this would take housing to an entire new level.