I'd agree that air over hydraulic would work OK. If you want to use the jacks to level the bus you will need more pressure than the 110# you mention though it would be enough to stabilize the floor so no one gets sea sick walking around inside. A hand operated 4 gang air valve would be needed to prevent creep down.
I opted for a completely manual hydraulic system. I repurposed 4 trailer leveling jacks replacing their innards with hydraulic rams. I ran 3/8" diam steel tubing from my 4 gang valves to a hydraulic flex line at each jack. My rams and pump came from a 4K# port-o-power kit plus 3 extra rams. A 10K# set would work better for a large bus (about $200 at Harbor Freight). The jack requires a reservoir which is easily made from a plastic oil can. When deploying the jacks you have to remember that hydraulic systems all feed the easiest load first so you must use the individual valves to equalize the load--pretty easy to figure out by looking at a RV spirit level as you go.
I'm sure you can improve some on my design but the price will be hard to beat. My whole setup came in at about $205.
Here are a few pics to get you started:
Jack
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