The sleeves I've seen so far ("green" and "yellow") are great, but I'd like to see, too, protectors sized for various larger card-stock components (e.g., Arkham Horror Investigator sheets). Are there plans to cover these as well?

Have you looked into photo sleeves?

I use 4x5" archival quality photo sleeves for sleeving up my Descent character cards and soon my WFRP character sheets.

It would be good for FFG to add to the range. For the moment, TBG has made some that fit Talisman Characters/Endings and Descent Hero cards. There is a thread about it in the Talisman forum.