Way, and I mean waaaaaaay too much maintenance. Don´t look at the Annual Failure Rate, but at the "Est. Time" entry in the design screen. Around 3 years, perhaps a bit more should be enough.
A Flag Bridge, as the name implies, is where your Admiral is sited. I wouldn´t put that on a regular Line-Of-Battle unit but only on a dedicated flagship or perhaps on a combat-jumpship.
Your ship is terribly slow. Personally, I go for 25% of mass (i.e. 1 engine per 1000t) for engines on missile ships and a bit more, up to 35%, on beam armes units.
Your armor is very strong. Perhaps too strong, if you have not researched at least 4 levels of armor (ceramic comosite, I belive).
As you noted yourself, the gauss cannons are pretty much useless
If you look at the firecon for them, you´ll notice a tracking speed of 32.000 whereas the cannons only track at 1.250. The thing is, only the lower of the two counts. Therefore they should match as much as possible or you´re either wasting resources (if the FCon is overengineered) or weapons potential (if the FCon can´t track as fast as your guns)
Your active sensor can see ships of 7.500t and up good, but has trouble seeing smaller ships and is virtually blind vs. missiles. A small res-1 sensor might help you out here.
You don´t have any passive sensors. This means, if you don´t want to notice an enemy only once you start taking damage, you´ll have to run with your sensors ON all the time. Trouble is, the sensors emissions are visible over a longer range than you can see with them (thinks submarines active sonar here).
A question aside from this:
Your FCon has a tracking speed of 32.000km/s, indicating you have researched Beam Tracking Speed 8.000km/s. To my knowledge, this should then also be the tracking speed of your gauss cannons. I am a bit confused here.
