Seems like an odd way to go.    Some comments:

1.   Symlin is especially recommended for diabetics who inject insulin at
meal times,  usually folks with severe lack of ability to manufacture
insulin..

 2.  Glucovance contains Glyburide which recommended for diabetics who can
still manufacture enough insulin to control their blood sugars.

 3.  Glucovance is a physical mixture of glyburide and metformin.      .

 4.  Metformin and Avandia are anti-Insulin Resistance meds for diabetics

 5.  Symlin is not an anti-Insulin Resistance med for diabetics

 6.  Elevated Insulin Resistance increases  the danger of premature heart
attack in diabetics.    Premature heart attack is just about the #1 problem
for Type 2 diabetics.     Replacing metformin and Avandia with Symlin may or
may not help control blood sugars but the replacement has the potential for
increasing heart attack risk.

7.  Byetta is a drug with some similarities to Symlin but is intended for
use by diabetics who can still manufacture enough insulin to control their
blood sugars.    It can be used together with metformin and Avandia.   IIRC,
it has produced some outstanding results used that way.   However,  I
suggest that it might be difficult to use together with Glyburide,  e.g.
with pure Glyburide or Glucovance.

It's difficult to argue with an endo but you might want to ask him to
clarify the Insulin Resistance/Heart Attack situation.

Regards
 Old Al