You can just ignore the update building. I OK now the little helmet looks stupid...but you don't have to update the building if you don't want to.
I created a very low-rent part of town--moved the buildings to a completely service- and specialization-free spot whenever I wanted to upgrade, and kept the neighborhood itself covered only by fire, police, and health.
Then I had another neighborhood that has the more "mid-century" homes, and a few estates. Covered by services, lots of specializations.
I'm getting bugged incessantly to upgrade the low-rent homes, but the nicer ones well-covered aren't offering upgrades at all.
I most definitely want the option to turn off upgrade prompts. I'm totally willing to have to pay simoleons or keys in order to upgrade a building after having turned it off, though.
Variation on the strategy some have already posted, but I do the following:
Build a new plot. Upgrade up to 1 upgrade away from your desired outcome. When you are ready to upgrade, make sure you have the plot in the desired land value (I was going for mid-level tier 2 homes so had to move to yellow-orange areas), and then upgrade it. IMMEDIATELY move the plot to somewhere without a road before it has a chance to offer another upgrade. (And no services too? Not sure if it helps but I have been doing this.) It will not offer an upgrade after that because it is not connected by a road. Once 5 other buildings have offered upgrades, then you can move it back and it will not be able to offer an upgrade but people will still be able to live in it.
When you do desire to do an upgrade on some other building, you will have to move it back into the boonies because it will be a high priority to offer an upgrade next and then you will be stuck with the little construction hat bubble and one of your 5 construction slots taken up.
Can be tedious to move large numbers of buildings (or delete large segments of road? that would probably work too) but worth it to be able to design little subdivisions. 🙂
