First I like your Ideas especially the last, but I have a few things to say.
1. That one Servant can produce more than enough food isn’t OP, as long as there is no need to let the crops and fruits grow (and having no specific time it needs to be harvested before rotting) one person can supply food for a lot of people. But implementing that even halfway realistic would mean, that every farming related upgrade would be useless for a long time before getting something from it and without a very good storage it would be even more useless for providing food, simply because it would need more time to grow the crops and fruit than it provides food for.
2. Focusing the mansion on something is basically something the player has to do him-/herself. If Maverik would implement a focus, there would be lost some of the freedom for the players. Also there are some players that enjoy being able to create something that could be called an arcology.
3. The last point would need to either have an additional shop in the guilds or a change in the prices in the reputation shop (alternatively a change to the rate one gets reputation). If the mansion-upgrades would be just added to the guild-shops you would need even longer to unlock the special classes or every upgrade would be unnecessary when unlocked.
P.s. please excuse if it’s hard to read or if I did some mistakes with spelling or wording, English is not my native language.