I'd charge you around $250 for a tube-driven loop. Prices vary by location and tech, but I don't think anyone would do it for a whole lot less than that. Reasonable range would be about 200-400, and some techs might not even do it because it's a PCB amp and a pain in the ass to mod. From what I remember there's probably enough room inside the chassis, but it would be a tight squeeze with the two channel model model. You could do an external loop, I suppose.
If you're going to spend that much on an amp and then spend more to modify it, then why don't you just buy an amp with an effects loop?
Rockerverb 50 man. Same general tones as the AD (with the gain backed off of course) with the added FX loop and reverb.

Also, I looked into that when I was going to buy the Rocker 30 head instead of the Verb, and a lot of people said that it took a lot away from their tone. So, Idk if itd be worth the risk of losing tone...and the ADs are beautiful amps, I wouldnt want to take a chance.

Thats just me though.

Other than that, theres a lot of external effects loops, but as far as I know they all come before the pre-amp so...
I really like the sound of the AD30. I heard the Rockerverb is a lot more modern sounding and I'm after a more vintage tone. Kinda like 60s psychedelic fuzzy/crunchy sounding. Only thing is I use delay with overdrive a lot and I hate the sound of delay before overdrive. I don't want my tone sucked though.
I got an AC30 but the speakers produced weird harmonics when I turned it up, also the loop on the AC30 is before the preamp. I may just check out the Rockerverb 50 and use it at lower gain settings and run a fuzz through the overdrive channel. Does anyone know if the overdrive channel takes fuzz pedals well when its at lower gain settings?