In BVR scenarios the heat signature and signature of missile being launched will be detected and from far off and the planes will easily evade them using evasive maneuver. Here maneuvering helps significantly.
Secondly, unlike F15, Su30 has 2 pilots which make maneuvering and targeting much easier than F15.
India has extremely rigorous training for IAF pilots. India does not need USA assistance to train pilots. Pakistan has got USA training while India has got USSR training and it makes no sense for India to give up the USSR training to go for USA training.
All these things are easily upgraded. Super Sukhoi is exactly for this. Buying F15 for electronics suite & BVR makes no sense as India is not much behind in developing these. Indian software industry is top notch and hence there should be no problem in making EW suites & AESA radar codes. India is also developing longer range BVR missiles after developing Astra.
India is getting Super Sukhoi upgrade for this reason. Once it is there, Su30 will have similar electronics as F15. BVR capability simply depends on the BVR missiles available. India has developed Astra and will develop Astra Mk2 with dual stage and SFDR to get better BVR capability. Buying a plane for BVR missiles is absurd. When we talk of a plane, we must exclude external items like pods, BVR etc as they are accessories, not the plane itself.