The Nanmo is rather underarmed and I don't think that Sonar is a workable solution.
By their very nature, FACs tend to be fast and operate in very shallow waters. The sonar makes both those things rather hard to do.
A small towed array is a better solution if you ask me. You certainly have the space for it. I'd also try to cram in some SSMs somewhere and at least one ManPAD launcher.
If you put a Towed Array on the poop deck and move the TTs forward to somewhere between the liferafts and the mg you should be able to cram in two Penguin launchers at the stern, outbord from the Towed array.
Also, you need more electronics. Right now, you only have a nav radar and a EO device. It's workable but not something I'd go to war with.
Here's an example of the kind of electronics you need.
From left to right you have a combined MF/HF/LF/VHF/UHF antennae, a backup VHF antenna, an ECM receiver (On the highest mast), a surface search radar, a nav radar, a gun director, a second nav radar, and while it's not visible, there's also a FLIR build in to the front edge of the bridge.
Another object of interest is the decoy launcher. (The second red thing from the stern)
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