I've done plenty of DWG migrations and they can be fairly straightforward and easy (can be).
AutoCAD Block Attributes can easily be mapped to Data Card variables. I would start there and test it out. Once you get that set, then you can drag/drop files in with more Data Card variables inheriting their Folder variables. You could even set up a staging area where you drag files in, let them update their Data Cards from Folder Data Cards, then move them to their final resting places.
First thing is to bring in the templates, XREFs and library files first. Then as you bring parent DWGs in, then you can use the Update References to get XREFs updated. This works really good for DWG files.
we moved all of our legacy autocad drawings into out vault when we migrated back in 2011. we didn't have xfres do deal with. but we did have some issues with block attributes. over the decades some files collected many different title block blocks. so a) we had to map variables to each of the blocks that were in used in all of the drawing. and b) had purge unused blocks from files (non purged blocks would still have attributes assigned, but they were not likely to have correct data in them).
if the AutoCAD files are "clean", it should go pretty smoothly (it took us a few months of cleaning to get ours ready to go in).