Well you did talk about quadrupling its capability in the same sentence as you mentioned the YJ-12 so the natural interpretation is that you are referring to augmenting the antishipping capability of the Sov.The addition of the universal VLS isn't so much about augmenting its anti-surface capability as it is about providing the Sovs a degree of tactical flexibility. You could retrofit the Sovs to become an arsenal ship or air defense destroyer without having to go to the docks; that would place them ahead of every single PLAN destroyer short of the 052D in terms of modularity. Moreover, these vessels are spacious enough to accommodate strike-length VLS, which I suspect will become more or less the "standard" aboard future PLAN vessels and MLUs.
The DK-10A is the most likely candidate for a VL, quad-packed SAM.
I think it would be a waste of a ship turn the Sov into an arsenal ship, which typically refers to a ship without the high end sensors normally associated with advanced warships but with an outsized load of VLS cells. It does not even have enough deck surface area for universal VLS cells to be considered an arsenal ship in the first place. 32 cells is hardly arsenal ship-worthy IMO.
As for tactical flexibility, I think it would be a possibility if and only if the universal VLS can load quad-packed MRSAM's. I know the DK-10 is usually thrown around as such a candidate but we have no solid evidence so far that the PLAN even considers this a possibility. Either way, even if the Sov is refitted with universal VLS I highly doubt it will carry HHQ-9 missiles due to lack of ability to guide them to their maximum effective range. It would load something like 8-12 cells of 32 to 48 DK-10's, 8 cells of CY-5 or whatever anti-sub missile is in use, and it would have 12-16 cells left for YJ-18 and/or CJ-10.