The Israelis used the T-55 chassis and rebuilt on top of it for their conflicts but that also meant they had funds allocated and expertise to do so.Simple problem here is that M113 will not survive the modern munitions. I won't specify it here, but its survivability is beyond questionable.
My thought is that Pakistan needs to develop a family of tracked vehicles based on mature AK chassis. These new types of vehicles shall slowly and gradually phase out M113s which can be re-fitted to serve support roles and or to equip territorial forces.
Another family of vehicles should be developed based on the Dragoon ASV. Look into the Canadian TAPV. The wheeled 4x4 vehicles to serve various roles including COIN ops etc.
The Chinese DF Mengshi vehicles are also a highly modular option. They already are being produced in almost 10 different configurations.
I think its not a debate at all. Its been settled during 1973 Arab Israeli War.
Israel has since developed heavily armored APCs typically armed with an HMG (now being equipped with a remote turret). As well as with heavy class of IFVs based on the Merkava IV chassis.
Egypt inducted M2 Bradley vehicles and also BMPs.
The reason i quote 73 War as a use case here is because it bears a number of similarities to our scenario with India.
There is a high focus on surviving for IDF personnel both from a limited numbers issue but also because of their focus on “dont die for your country, make the enemy die for theirs”.
They also had access to decent powerpacks that could replace the transverse one on the T-55 to make space in the compartment.
technically Pakistan could convert its legacy tanks but even if funds were made available from cannibalism from other programs the issue is lack of expertise in doing so for chassis beyond the M-113(which is a simple design in general).
Bear in mind the Israelis still use the M-113 (some 500 active and 5000 in storage available for conflicts) for APCs and while they have numbers of Achzarits (~200) and token numbers of Namer(120) and Nagmachon(specific for Urban warfare) those are generally kept for offensive ops.
The reason for this is that the offensive ops are for IFV and Heavy APC while the battle taxis remain the M-113. None of the 40 ton APCs types IDF has are as mobile as something like the M-113.
The Namer will eventually become the standard but even then the focus has shifter to improving survivability by Passive and APS systems rather than layering on Armor.
If Pakistanis can afford it - the PA could get a small number of Turk Tulpars to support offensive operations.
As far as better ATGMs go, the PA has a great option in the SK Raybolt if they can afford it.