It isn’t meant to intercept everything, just something, rest could be left to more conventional BMD. Kazakhstan in NATO sounds fun tho.
Road-mobile ICBMs, well, they are based in particular areas and Topol can only launch from a relatively small number of pre-determined sites, no idea why or on what’s the situation with Topol-M or Yars. Some are based close enough to Belarus to be in range of this proposed system, Belarus in NATO when
They only carry one warhead through, credible answer is to intercept the warheads outside the atmosphere, non-credible answer is to build a ground-to-ground strike capability into my system, then watch the launchers from orbit and strike before missiles are fully erected.