You could do it if the sight perspectives are only from that of an individual, but that has it's own issues. It kind of depends what kind of experience you want, do you just want a digital tabletop which seems like what they're going for, or keep things hidden unless you can see it. Keeping things hidden from the players was one of the few advantages of Roll20 and it was kind of cool to literally keep them in the dark. I think at least at first they're going for the digital tabletop.Yeah. That can be especially tricky if you start working with sight lines on the map. Getting the sight lines on different, overlapping maps (if you want to do a multi-story location) is honestly more trouble than it's worth. Much better to just have the different levels on the same "map" and then jump from section to section, if you follow what I mean.
But even then there are issues because the DM needs to see everything. Line of sight works okay at the individual player level but it's much more difficult if the DM needs to track multiple minis for both monsters and PCs on multiple levels.