There's a few things to say here:
First, a diplomatic ship will usually need to be basically permanently parked somewhere in order to build and maintain diplomatic relations. This means that having it as a military vessel is somewhat troublesome, as it'll eventually need to have its crew rested and, more importantly, stock up on MSPs. For that reason, it's usually best to make them commercial vessels.
Second, it's better if possible to have the ship weigh 10k tons or less. I believe if a ship has a diplomacy module, aliens effectively count it as being 10K less in size for calculations regarding diplomatic penalty introduced by the ship potentially being in a system they'll claim. I can't find the exact place where this is stated, but check out the "Diplomacy" section of the index:
http://aurora2.pentarch.org/index.php?topic=10666.0Third, from a purely mechanical perspective, there's no point having the resolution 1 active sensor as the ship has no defenses against missiles. For similar reasons, there's no point having two layers of armour. If this ship gets in to a firefight of ANY kind it WILL die. There's no point even putting CIWS on the ship, as you'd have to put so much on to give it a chance that you've basically created a point defense warship that happens to have a diplomacy module. Of course, you are welcome to add these things from an RP perspective - who'd want to be in a defenseless tin can going to talk to potentially xenophobic aliens?
Lastly, it looks like you have an order of magnitude too much fuel on the ship? I don't know how big your galaxy is, but 250 billion kilometers is a HUGE distance, one that I've never even got close to needing.