Bry,
The way I see it, in the situation that you are portraying, you'll have a slim window in which to jump back in. You're not competing against guys who have the same experience you do because 90% of them are already on a list and waiting on recall. After that happens, I would guess that the first airlines who hire will probably be attracted to guys with 121 time. These guys will have the same experience you do and probably have the same lack of recency that you do. Basically, you'll look identical to a furloughed guy from another list. After all those former airline guys are picked up, they will probably turn to CFI's. I believe that by the time this happens, your ship will pretty much have sailed because the mins will have gone down and you will have been basically out of the game for that much longer.
When comparing you to the 10% of former airline guys that you'll be competing against, it may be better for you to have an ATP, but I would guess that most of these guys won't either. Its hard to tell if it's worth the time or money for the tick on your resume. I'd probably say that if its not going to cause you financial hardship, go for it. If nothing else, it may allow you to be hired at the beginning of that 10 % instead of at the end, and we all know how much being up the list 10% can up your QOL.
I understand that my %'s may be off, but thats how I see it going down.