This I found a bit poorly thought through too. I thought it strange that Revan apparently started sporting his/her dark robe, hood and mask before actually becoming the Dark Lord of the Sith. Remember the ruin cutscene from Korriban, when Revan and Malak enter the temple for the first time. Malak's lines give away that they have not yet fallen or become Sith, but Revan doesn't exactly look like your typical canon Jedi, does he?
I thought this was explained well enough in K1, but K2 dismissed the Star Forge for convenience (in the case you chose Revan to have been dark). The Star Forge simply helped them amass their huge starfleet, but Malak tells you in the end that Revan never realised the full potential of it, that he merely thought it to be a factory of sorts.
Very good ideas. The only thing that seemed to change with your level of influence was the characters' physical appearances, which was a big let-down.