Hello there. As the title suggest, I have problems with the amount of impact 1 or 2 mermaids (Cybran T2 Stealth-field boat) can have on naval fights.
I'm a complete noob rated 900, and I mostly play custom games. I got a lot of setons under my belt, and the oh-so-mandatory-for-noobs gap games, but I enjoy 'real maps' here and there. I do prefer larger team-games, and I like maps where all 3 theathers of war are present (I actually enjoy navy the most). So there's my bias.
To further emphasize my bias, the example of a game I have played out on Setons: https://replay.faforever.com/18963421. Now, for the most part, you can ignore the first 32 minutes or so of the game (though you'll see I struggle plenty with stealth boats), and focus on the T3 stage, mainly after I loose my navy and my air player loses... everything he is worth for.
Now, I am quite aware (even at the time) I was, from the point my last Neptune fell, very much on the back foot. Yes, I didn't win the large naval battle that took place, given how 4 battleships were left standing, as well as a carrier and a couple of destroyers, but I was definitely not out of the fight. I had 2 Summits rolling out, and I knew the remaining battleships were somewhat damaged - 1 was almost out, 1 was solidly damaged, and 2 weren't squeaky clean either. So I planned to leverage the Summit's superior range to try and take out the two more damaged battleships and preferably the carrier as well. Well here rolls in a single T2 Mermaid. And I can do nothing. I can spam scouts, for sure, but those don't give enough time for my ships to lock on and fire. So instead of me being able to at least gain a tiny bit of ground back, I am completely helpless. Sure, I got T3 Omni Radar in the base, but that won't help. Even if i had a T3 air factory (or could rely on spy planes from my ally), the intermittent signal would simply not allow me to do anything. Because ofc there will be most likely some Cruisers in the area (especially given how strong Cybran cruisers are and how they benefit from destroyer-range battles, unlike MML cruisers).
Again, I'm well aware it was an uphill battle, and I could've done a few things better, but I think my situation got 5 times worse because of 1, later 2 mermaids and the T3 sonars stealth field (won't even bother trying to understand sonar's stealth field range - why not just make it as large as the T3 radar range fml).
Anyways, enough of the 'rant' part and explaining my viewpoint (though I would recommend, if and while watching the replay, to slow the simulation down just to see how bad the stealth is from my point of view). My suggestion is that the torpedo defense on the mermaid be removed or severely nerfed, and/or have its power drain increased (out of the pocket, I'd argue for 500-1k energy per mermaid).
Stealth is, I'd argue, the strongest anti-intel ability in the game. Some might argue that cloak is stronger, but I'd beg to differ - most of information you gain you gain from the radar blips when zoomed out - and stealth wipes those. But it is somewhat easily countered - you get an omni. Except, in the naval situations, you can not get an effective omni coverage because enemy is on water. And you might think that it is not such a big deal, but all other units use stealth for one very obvious thing - to get in close to use their strong weapons. The Mermaid gives this same stealth ability Destroyers, Cruisers and Battleships - units with some of the highest ranges in the game.
You could argue for scout/spy planes, but in any kind of semi-decent naval army, you'll have AA that will kill those, so unless you have a constant stream of them, they won't help. Also 1 Mermaid is ~ 3 Spy planes, no way you can do anything useful in a large battle with just 3. In naval terms, there is no intel-counter whatsoever to stealth. So the only way to be able to fight it is to kill the Mermaids.
But how do you do that? Because of the stealth, it's very hard to get an accurate read on the current positioning of the enemy ships, and you are kinda left with 2 options. Go all-in so the stealth doesn't matter because armies are in each other's vision radius, or try and snipe them. So you'd think that T2 torp bombers should be an awesome solution to the Mermaid. But of course, not only is it hard to target it in the first place (because if it's moving, good luck actually getting to see it in the first place), it also has torpedo defenses, so you need like 5x in it's mass worth to actually kill it with torps (because, remainder, the enemy most likely has Cruisers).
Alternative solution (difficult):
Another thing that could be done is have the stealth boat have 2 operation modes - Silent stealth and Loud stealth. While in silent stealth, the stealth field range would be much smaller (say 1/5th range), allowing for the stealth boat to cover only a couple of units. While using loud stealth, the stealth field range would be large (as it currently is, or heck, even larger), but the boat itself would be un-stealthed (even if under cover of other stealth fields, like for example other Mermaids). This would still allow for it to pull of small stealth flanking actions on maps with more spread-out naval battles, but you'd need a lot of them to cover a large fleet with it in this mode. Or you could have it cover large areas, but then the Mermaid itself is visible, so the enemy has a chance of maybe more easily countering it. Though this would probably be very hard to pull off, if even possible (having a unit ignore stealth-field benefits while being in one).
The Jammer Disclaimer:
Some might argue that UEF's jamming is 'as busted'. And while that has nothing to do with my post actually, I'd like to address that non-argument with the following: jamming is only effective up to a cap of like 20 units, if we are talking large naval forces. After that, the density of the units simply results in 'fake' radar blips aligning with actual units. Stealth, on the other hand, get much stronger the more units one has. In addition to that, at least with jamming, your units will keep on firing, so they might make a random hit here and there (not to mention take down your Bulwark's shields "for free" - UEF jamming is the perfect counter to it's own Bulwarks), while when enemy's units are stealthed, your units are sitting pretty doing nothing.
Mermaids give the strongest anti-intel ability to all of the units in a very large radius - stealth. Because of its location, that is the sea, there is no intel-grade counter (like the omni radar for land), so you have to rely on killing off the mermaids instead of countering it's anti-intel.
But one can't even do that effectively because there are two options - torpedo bombers (or subs, sure), but it has a torpedo defense, or clashing your army and hoping you are not even a tiny bit behind in army size, otherwise you loose purely to army strength (even if the enemy decided to turn off stealth to make it easier for you).
I suggest drastically increasing their energy upkeep for the stealth field, and/or nerfing/removing their anti-torpedo capabilities. Another wacky idea is given in the 'alternative solution', but it's probably not possible, so meh.