I would not say it is unreal to have 8 AIM-120's on a F-15. It depends on the mission scenario like some already said above.
http://www.fas.org/man/dod-101/sys/missile/amraam-990493c.jpg
Like F-16's sometimes use 4x AIM-120 without AIM-9's on the plane. And also, I believe 6x (RL) AIM-120 quit enough for any enemy aircraft, to scare him away or even shoot him down. If you have a RL F-15, against some old russian hardware, from some countrys.
I guess if they would know the enemy is useing SU-30's or what ever, I think they would carry 8x AIM-120C's on the F-15's, through the fact that the rule of engagment in this case would mean BVR only on such enemy's, and any merge has to be avoided.
But don't forget in FC2.0, we have MiGs with 6x R-77, flyeing around as well.