It's funny when You describe this in that style when Ajrun gun don't look to be better then KBA from Ukraine (pak. T-80U) or we consider that Idnian army havent AFSDS able to kill frontally T-80UD or ZTZ-98 tank. IMHO its even more funny when we look ad avaible in India tank ammo...
Its funny because you don't know about the context of the program and hence end up finding things amusing. The Arjun FCS+ Gun combo can take far more modern rounds than it currently has, and the answer to that is simple. GSQRs- the Arjun team had no incentive actually a discentive, to go beyond the GSQRs when the base line Arjun was not being ordered! In contrast, the modified GSQRs were very emphatic on FCS performance including fire on the move. In the mid 80's itself, based on a mishmash of Janes and Brassey's the IA wanted 90% Pk from moving Arjun to a moving target. Such implausible requirements are the bane of Indian design efforts because they delay programs for decades, since the Army/AF in particular lacked design engineers with experience in technology and are highly dependent on 3rd party sources like Janes to know what is current tech,. beyond the earlier gen stuff they got from Russia! Today with many officers cutting their teeth on such programs, things are better, but still the Army is a vast organization and problems remain!
Net, after the Army accepted the Arjun MK1, which met all GSQRs, and series production was launched, the finances became available (as there was a tangible ROI) to develop modern ammunition beyond the late 80's genesis of the FSAPDS! And the FSAPDS itself was not asked for to be improved. The Army asked for an improved FSAPDS only after the Arjun beat the T-90 in trials and DRDO itself realized that it needed to put newer rounds in, lest all the other effort go waste. Hence the rush to qualify the LAHAT as well.
In those opinnion I was based on previos post about Kanchan in this topic. And mix RHA, ceramis and light aloys plates present in those posts was base for that opinnion.
Sorry, but that opinion is still an assumption, because what is in Kanchan, the latest version on the newer Arjuns is still classified. The light alloy, composites, RHA stuff you are mentioning is the same that was first released about the armor way back in 1995! I leave it to you to discern whether things are the same today after all those year.
The same description for the Arjun is given in 90% of the talks as well.
Please note DRDO has no incentive to release such information beyond the bare minimum of jargon. The reason being no matter how good or bad you and I may feel about this, they only have one customer, the Indian Army. None of their items, hitherto have been for export. As such, they completely lack any PR sense & only after this was heavily expolited by a sensationalist media, have they even endeavoured to develop basic stuff like websites. And nine tenths of that stuff is the same I saw when the sites were first launched in 2005-07. Like it or hate it, this is how most Indian defence organizations work, with a customer that hates it when information is released. Further, all that matters to them is that whether the product clears trials. After that, only can orders be expected after all.