On the surface, getting 2 CLAA's seems great for IJ, but as Loka notes, they are actually quite anemic. All of the CA's are better.
They have the same number of 'heavy' AAA as a regular CA (all that counts when defending other ships in the TF), and CA are like hens teeth for Japan. They just don't have enough CA's and none are built during the game.
Even if you convert all the CM that can to E,
Those CM's that convert to E's will still load/carry/deploy the type 93 mine. I use two often as they carry 50/60 mines respectively. Those are about the largest minefields I lay. Prefer multiple fields in a hex as the only ones that are effective are those that are unknown.
Though, given the number of To'su-s in the roster this is gamey indeed
Not so. For whatever reason this was incorporated intentionally, and as said they are the least effective Japanese mines.
Having the Tenryus around to do some minelaying is also useful. They're much faster
Definitely a factor, depending on your style of play.
offensive minefields in contested waters.
Problem with 'offensive' minefields is that in deep water they decay very quickly, and I've had 'no joy' employing them. OTOH I for one, and would imagine my opponent in a PBEM as well, avoid shallow water hexes in many instances. Only time I don't is when I've no other choice or I know/suspect heavy sub infestation.