With regards to alkalinity stability and calcium hydroxide, the problem is not the limewater itself. The problem is the delivery mechanism. Most people's ATOs work well enough for keeping salinity stable. However, they're not great in terms of adding the exact same amount of fresh water at the exact same time every day. Evaporation may also vary based on time of day, season, how much your AC has been running, if/how much you have your windows open, etc. You would have the same problems with stability if you mixed sodium carbonate (soda ash) or sodium bicarbonate (baking soda) into your ATO reservoir.
If you want to use calcium hydroxide in the most consistent way possible, make a super-saturated solution (or use a kalk stirrer/reactor) and dose some limewater every hour on the hour with a quality dosing pump. You get the same amount of calcium hydroxide dosed every day, regardless of how much your tank evaporates. If you're dosing less limewater than your tank needs in top-off, your ATO will pick up the slack and add freshwater to make up the difference.
The only caveat with this approach is that it's possible to add more limewater than your tank evaporates in fresh water. If this happens, however, you will notice your tank's water level rising and can adjust accordingly.
