If you have the remote controls for them, it should be possible to use cheap Broadlink devices to control them. There is a community-contributed driver written by @cybrmage to locally control Broadlink devices (and they are relative inexpensive). The trouble with IR control is that it is one-way. So your renters may manually adjust the thermostat on the Benelux units and there's nothing you can do about it.
For genuine two-way feedback control you would need to use @signal15's suggestion.
Plenty of Hubitat-supported locks. There are fewer complaints with zigbee locks than z-wave. Schlage locks are not on the compatible devices list, so avoid them.
