You seem really serious about it and I thought my lame joke would be enough to deter you. Damn!
Of three vessels, two have already suffered severe damage. Though one have managed to rejoin, one's still missing. The remaining lucky one got a MLU worth 300Cr...to just switch from steam to diesel.
Even if hypothetically all three vessels are restored and fitted with up-to-date propulsion then also you'll be left with multiple issues. You've got just 16x Kh-35 (apart from range the biggest issue is limited stockpile), 24x Barak-1 (good last layer ADS but pathetic to have it as primary ADS for a 4kT vessel), your radars are still 15-27rpm rotating ones, the max range for your Fire Control Radar is 30km
If you're really concerned about cost and want maximum bang for your bucks then you can probably get new, modified Saryu class patrol vessels relatively cheaply compared to [salvage + repair + re-engine + electronic/weapon upgrade] of an antique hull.
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That's Nilgiri level of loadout...
Interestingly, Saryu class patrol vessels are perhaps the most stealthy design after Shivalik class.
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Add panels on the mid-ship RHIB area and you might get better RCS than Shivalik.
On some days they'd cry because their 8x BrahMos - 32x LRSAM armed boat is under armed and on other they'd root for a Barak-1 armed boat...the life of a typical Indian Navy enjoyer