Well, just a roll-in rack is easiest if you don't want to lift any bikes. But if you can lift bikes to hang bike by the front or rear wheel (probably alternating F/R so adjacent handlebars don't clash), I've seen online racks that attach to the wall (I don't know if one rack for multiple bikes or they are all single and you just put up as many as you need), and when the bike is hung, they swivel left and right, like rugs hung up in a store, for easy access to any bike, but then all store compactly against each other, either straight out from the wall, or all swung closer to the wall to save space. The wheel hooks adjust in height so for each bike, you don't need to lift far up off the floor once tilted up vertical. Seems like a smart system in both respects.