So, just do it.Silos are not "difficult" to build, they are "expensive" to build, two different things. Also we do NOT have any Peacekeeper silos left and the Peacekeeper motors are not usable for long-term silo use anymore. The Castor 120 is based on the Peacekeeper 1st stage but its not the same and would have to be modified for long-term silo use.
China is beating us in the IRBM and MRBM arena due primarily to INF. ICBMs they are just now getting close to what we've have for decades. Russia is merely updating their current inventory and replacing their Soviet era missiles. Topol -> Topol-M/Yars, Satan -> Sarmat, UR-100N -> Topol-M/Yars.
LEO trajectories are faster but they are less efficient -> less payload available.
If you are adding heavy decoys to the HGV, it has to carry them the whole way, making it even larger, and they will be useful for only a short amount of time, that's even if they can match the RCS of the HGV and its huge thermal signature.
So you now want to add sensors to the HGV to detect an ABM? More cost, more weight, more complexity. I don't know where you are getting this Mach 45, the HGV won't be doing Mach 20 in the terminal phase, Mach 5 might be closer, it takes energy to glide those ICBM range miles. Evasive maneuverability is a factor of G ratios. If the interceptor can pull 60 Gs, the HGV needs at least 20 Gs to escape, that is asking a lot for a vehicle that has been soaking heat up for a long time and is already thermally stressed. Note also the HGV is limited to aerodynamic control, while the interceptor can also use TVC.
We have to match Russia's overall strategic capability not specific tactical capabilities, and yes the SLBMs also play a part in that.
So Russia is operating 4 ICBM types and 2 SLBM types, updated to carry 24 warheads and HGVs. Only for sanctions, they'd be building the RS-26 and a new missile train and missile too.
Only if you don't build a bigger missile.
You could have the sensors off board and communicate with it.
You're confusing g's with time response.
We ain't even close to matching it right now.