... in some
areas, I've completely peeled away the stucco, exposing cement, in
other areas there is a very bumpy 1/4 inch high stucco layer which may
or may not peel off later.

After reading your replies, I think that I'll (1) attach a very
coarse sanding bit to my drill, go over the remaining stucco to even
it out and to expose any other areas which might be loose. (2) I'll
notch out small sections in the remaining stucco areas so that the
cement underneath is exposed (maybe even create a hole into the
cement) every 4 inches or so. (3) I'll apply a chemical that
increases bonding, then the Thinset and bricks. How does that sound?
Maybe it'll work? Kinda, sorta?

Cindy