Single Frame OH colony

Seems like it should be simple but my guess it's not. Harder to keep in balance (like your moniker). The ratios of various brood and bee age demographics is a finely tuned system. Pheremones trigger supercedure, swarming, organizing hive duties; ie. honey vs pollen gathering, temperature and humidity control etc.

I am just speculating, but many things dont scale down well.

No, a single frame observation hive is too small. If you want to keep an observation hive all year long, it would be best to have 10 frames if it is going to be your only hive. Most people have trouble keeping an observation hive with anything less than 8 frames alive. That being said, if you were an experienced beekeeper with experience running observation hives, it is possible to keep a 2 frame observation hive going if you have other hives. I run a 21 frame and a 2 frame observation hive all year. It is easy to keep the 21 frame going. The 2 frame hive is way too small for a full sized hive and wants to swarm to death in the spring/summer and can die out easy in the winter if not taken care of properly. Betterbee sells a 5 frame observation hive that could work if you devote yourself to learning how to run it and have other hives to swap frames with.