To apply your analogy, 30mm is pistol; 100mm low velocity is PDW; 105mm high velocity is 5.8/5.56 assault rifle; and 120/125mm is 7.62/308/6.8 battle rifle.As I've said repeatedly, the ZTQ-15 is unsuited for a tank-vs-tank combat but even engineering troops and MPs are given PDWs so they can at least make a modicum of defensive effort when attacked.
What I see right now is that the ZTQ-15 is being given a pistol for dealing with a MBT. I'd rather it be given a PDW; it'll probably still lose but make a better showing of itself.
What I'm asking for is not a substantial redesign of the ZTQ-15, what I'm asking for is just a further upgrade to a gun-launched ATGM in the PLA's possession with other technology already in the PLA's possession.
Your obsession with having the newest and fanciest tank launched missile is even more misplaced given the fact that PLA mech infantry tactics involves combined arms as standard, meaning 15s could expect to have mech infantry support as standard, which includes dedicated HJ10 launchers.
15s are meant to add additional punch and durability to IFV scouts and flankers; they will be the spearhead top help punch through similar enemy IFV formations and take 30mm/100mm LV rounds that would ruin the day of friendly IFV on the chin and keep going. If they encounter enemy heavy MBTs, they pull back and call in the Calvary in the form of friendly 99s or long range ATGM support from HJ10 carriers.
The only time 15s are supposed to actively engage enemy MBTs is as part of a combined force and after it has managed to successfully flank the enemy, and will be coming in to engage enemy heavyweight MBTs from the flanks or rare as friendly 99s are engaging them from the front.
15s are meant to work as part of an integrated system when you are obsessed with trying to make it fight everything under the sun by itself.