But Glen himself would not neccesarily have to appear😉(you know, seeing as how he can't)
If they did in a form of sequence, say...a sequence of visions, each of them could appear to Angel in their own way.
Cordy could appear as her self, while Doyle could speak through somebody else...he could posess Wes...we already know that Alex is good with accents, I'm sure he would work on an Irish one😉