Currently, you can make just one select object live so to be able to work on multiple objects you have to combine them all together and then separate again, for example when you use QuadDraw tool or when you want to quickly project one mesh on to the live one, and things like that.
Combine/Separate "workaround" to work on multiple objects is not quite ideal, unfortunately, so it might be ok in very early stages of modeling, block out, concept art, etc. but often time in bigger production (but as single artist at home) you might have your scene more organized and often also very complex hierarchy set and fixed (for rigging/animation purposes) but you have to still do something so you can't really just Combine all objects and kick them out of hierarchy just to quickly use tools like QuadDraw or project mesh on to the objects and then Separate objects and then find where there were back in that same hierarchy.
Another solution, which i often do, is to just duplicate and then combine those objects and use that as a live mesh but then you have double mesh which is not that bad but still not really streamlined and clean workflow.
Suggestion:
1. Make Live to be able to accept and make live multiple separated objects at once so that you can use tools like QuadDraw or/and project objects on all live objects at once.
2. Additionally, if not too much of a trouble, to be able to add a group which might have multiple objects inside and all objects inside that group would become live.
Ideally, it would be great if Maya Make Live tool has also something like 3ds Max Placement tool too > https://www.youtube.com/watch?v=ePmIAoT2p58&list=PL_6ApchKwjN_nyXQX075MZF2ivDI_Bd8H&index=6
where you would, for example, RMB click on that magnet button to quick access options like what 3ds Max tool has.
