So we have all these wonderful houses and wonderful furnishings, but we can only show off one of them at a time (without addins). That seems crazy to me, considering that houses seem to be a major coin and crown sink for ESO, so why would they not let us capitalise on that by showing off all our creations?
My suggestion to solve the issue is to create a configurable portal or door for us to place in our houses.
How it would work: When you place the item in your house, a dialogue appears which allows you to pick one of your existing houses. After placement, the furniture item works like other portals and doors in ESO, but instead transports you to the front entrance of the chosen house.
Not only would this allow people to visit other houses by creating a 'lobby' house with portals to your other houses, it would have huge benefits for guild participation in labyrinths, treasure hunts, parkour and other guild events, as they could now span multiple homes instead of just the one. I've seen some very clever and fun uses of houses for guild events, so I can only imagine what interesting things people would do if they could use multiple homes.
Bonus: The portal doors themselves would most likely be a premium item, either in the crown store, or through the master writ vendor or as an achievement award etc (or all of those options). I imagine it would be easy enough to make a bunch of different types are there are already many, many existing models for doors and portals in the game. But I do think at least one basic type should be non-crown, as it's real value is in encouraging people to buy and decorate multiple houses, so you don't want to discourage that.
I suppose you could also have portals that go to other people's houses, but issues with permissions etc might make that less practical for guild events. It would be nice to have a portal to a guild house, or between a guild house and hang-out house, especially if they ever give us any interactive furniture that makes hanging out in houses more fun. But I think the first and easiest step would be portals between our own houses.