The reason I doubted the worth of differentiation between beastkins and halfkins is because there will always be a very limited amount of beastkin images available (I think). Therefore, even though it cuts out realism, it might be worth more to not differentiate them, thus allowing for a much greater variety of images for beastkin. That was my reasoning, though I should have explained it.
About the scans time Im genuinely surprised it acts that fast even though its just loading the files names. Right now Im just using the MGQ pack for testing purposes so I literally felt no lag at all. My concern was due to slow loading times of the portrait menu when you have a large size of portraits but that's normal since its loading all the images entirely. The last feature you mentioned sounds really awesome for curiosity and debug purposes. It would absolutely come in handy when testing out new packs before the completion of this mod and its a niche thing to have at all times anyway so Im all up for it. Thank you again for working on this, Im really looking forward to the future of this mod.