They have been designed with unguided bombs in mind though. Look in some older books and you'll find Mk's listed for the F-15A. It's just fitting a different set of rails AFAIK. So slapping two JDAMS or SDB launchers wouldn't be a problem, weight wise at least. And the radar was already dual mode, right?
This could come in handy if you have C's on patrol over a battlefield for CAS. But indeed, why would you with the F-22 being capable of the same and plenty of E's around for at least as long. Not to mention the SH.
I think you have to look at it more from an awareness point of view. Far better awareness of what's facing them on the ground. A2A Fighters have been targeted on no-fly zone reinforcement sorties from the ground. All they could do is turn of radar and bail, without knowing anything other than direction of the threat.
The Brits fitted ALARM to their F.3s (by trial) because the F.3 already has a powerful Emitter Locator System. AESA will give that possibility to the F-15 and then some. Low probability of intercept radar, plus simultaneous AA and AS scanning. AGM-88 is like the AIM-7, so let's say 2x AIM-120, 2x AGM-88 on the fuselage, 2x AIM-9 on the wings. That's isn't a heavy load.