Just going from memory here, but IIRC, some of the AES (AES-10) don't have the thicker barrel of the AES-10b. And I don't know whether the thinner AES-10 barrel is equal diameter to WASR barrel, but if it is, all you'd gain there is a longer barrel (which may be what you want). If you're considering the thicker, heavier barrel, I don't think there's any practical way to make it fit.
Centerfire had a few AES-10b earlier this spring ($799) and I sort of regret not grabbing one before they sold out (memories of prices two hundred less were still too recent I guess). I've read bad things about the AES-10. Best option IMO is keep the cash for an AES-10b on hand for when one becomes available. Good hunting.
First question you want to ask yourself is what do you expect to get out of it.
Somewhere along the line you need to ask can it be done within reasonable costs and effort.
All of the WASRs that I have seen are 1 mm thick stamped receivers. I would not put a longer or heavier barrel on such a receiver since the receivers flex quite a bit on a stamped European AK. I did not mention the Chinese since their receivers are thicker.