UEF T2 Navy stage currently suffers from "Pre-2018 Seraphim T3 Land Syndrome." Mainly, it requires completely optimal unit mix/unit micro gameplay in order to just barely edge out a decent trade against factions that are rallying a single unit (exodus, phim destro, trident, barracudas) at you. And even then, you don't win against half those units.
To adjust that I propose the following doctrine for both UEF navy and Seraphim navy to make it way more intuitive to use and interactive without ruining the ability for any faction to play in the pre late game navy.
Range: 50 -> 80
Speed: 6 -> 5
The intent here is to make the Cooper the UEF variant of a sniper bot, except it's more focused on baiting poor engagements than high alpha strike. The idea is that Coopers are weak, they need bulwarks and cruisers to keep them safe. They are also quite slow. I made them the same speed as Exodus and Salem as frigates exist at speed 6 and I figure this would encourage Aeon to do something besides Exodus spam in order to catch coopers out of position. However, neither has a range advantage over the other so Exodus is still perfectly capable of stagnating map control as is Salem, but that plays into the UEF desire to tech switch into early T3 navy if the enemy allows it.
I'm willing to see the unit nerfed in damage output as well, but I have no idea what good values would be for that.
Mass: 2250 -> 2000
This one I'm not sure about. With the upcoming buff to Valiant, I do not know if it would need any further buff to fill the role it would operate in here. Mainly, it's the teeth that puncture anything trying to touch the Coopers. They do not need extra hp from Bulwarks because they are meant to cut off units trying to push into you while the Bulwarks retreat to protect the Coopers and Governors. The purpose here is quite reminiscent to pillars and so I propose a small mass cost decrease in other to make it easier for UEF to actually get their unit mix synergy going while also making Valiant just a touch more viable against their mass in frigates.
Speed: 5 -> 5.5
HP: 6900 -> 7200
The above changes makes UEF actually interact well with Aeon and Cybran and force all these factions to adjust their unit mixes during naval combat. However, the problem is that Seraphim is left out to dry.
In order to rectify this I propose buffing the speed of the Seraphim destro, which will also apply underwater, and therefore make it viable to snipe coopers by catching up to them and surfacing. Once the coopers are dead, the Seraphim destroyers have free reign to handle the Valiants due to their terrible torpedoes and can even retreat to choose the next point of engagement. I included an HP buff in the case that the speed buff would not be enough, but I did not want to go too crazy with it since the central thing is tanking the initial Cooper volleys.
This also has the side benefit of giving Seraphim a response to the higher range destros since they can actually catch them now without a frigate swarm.
All in all, frigates are still faster and can catch all these destros, but differentiating the destros further while also making the UEF actually equal more than the sum of their parts will greatly improve the pre T3 navy stage.
I did not speak much of Aeon and Cybran because I think it's self evident what their navies want to do. I hoped to encourage Aeon to make frigates more with this idea, but beyond that I do not have a huge problem with the doctrine of either of those factions.