1) there are early-stage plans to rename files based on tag info, but the implementation won't happen in the short-term. the problem with this feature is that so many different people will have so many different ideas about all the features they would like from renaming files, so we have to refine it and come up with the best solution to satify the majority.
2) 3500 files from an external source will probably take quite a while, try adding 350 files and see how long that takes, and then multiply it by about 10 to see how long 3500 files takes. the file sizes shouldn't matter, only the number of files. and if your USB connection is only USB 1.1, then that may blow out the amount of time it takes to load them.
for me, loading about 1500 files from my local drive took about 5-6 minutes. try loading files from your local drive to see how long it takes on your computer, its a good experiment.