It will defeat the purpose & won't be cost effective. As the missile development cycle goes, below iteration is standard practice
so for a tactical battlefield missile, the aim is to be cost effective while having high degree of accuracy & being able to operate in tightly fought over battle space. That means working in dense ew environment, having counter to enemy jam/spoof effort , able to defeat enemy AD and being undetected as much possible with very short mission time. Battlefield AD systems cover altitude upto 18-20km at best , 25 is a stretch. So your Rudram needs to be flying just above this zone, fly fast and conclude mission within short span.
So why would you want to send it up to edge of atmosphere at 70km ? This would mean enemy OTH radar will be able to track it & be aware of it much ahead of time. Second point, to send it up to that altitude you will need a bigger booster ie heavier missile, not suitable for air launch.
Then even if you have made it glide from an altitude like 70km, the acceleration gained will be much greater than the thrust provided by the 2nd pulse itself ie the 2nd pulse motor will be useless. If you already have high acceleration due to coming down from 70km above, your airframe will generate some aerodynamic lift, enough to make you glide at high speed if there are suitable control surfaces. So the 2nd motor will not add to this kinetic acceleration and enhance it. Therefore you can only cover a 100km or some more but not go from a 550km range to 1000km+ range. To cover such distance , your rudram has to be bigger & differently conceptualised, or use something like ramjet/scamjet/turbojet etc propulsion.
Then comes the weapon delivery system method, explained in below gist , which is another challenge on its own.
