Presuming you could make it targetable and are facing a Titan...

2 Radiances + 2 Raptures + 1 (or more) Progenitor + Dominas.

Animosity+Vengeance with healing from the current target while the other knocks away AM with DAM (I would like to see this).  The enemy Titan suddenly has to deal with a well supported ship probably healing at 25 hps and 40 sps with EAA converting damage into AM to return fire on the titan.  As one starts to get low, alternate to the other.  I don't know how high Advent mitigation can go in rebellion, but combining that with EAA, against something without phase missiles, this will be one vicious anti-titan (or starbase) combo.  You'd probably lose one or both Radiances in the battle, but presuming that you have your own titan in play, it would significantly increase your chances of winning.

Vengeance against a titan would be quite impressive.  This also assumes that it can reflect damage to a titan.  I'd assume it can, and if so, that's going to make it hurt to go up against such a synergy (something the Radiance hasn't ever been involved in in MP and only was in SP before the Malice nerf).

Taking away telekenetic push from the Halcyon will break the advent because they need bombers from halcyons to survive the early game and also a way to put there enemies at a disadvantage. The radiance does not field any bombers.

• However the radiance is a class B capital ship
• All battleships are second openers for the advent.
• If you bring it as a third cap it will die because it hasn't leveled up and is dealing with mid-late game enemy fleets. 

Benefits of the radiance:

• Its low cool down on detonate means it can disable abilities from multiple tec or vasari carrier caps like scramble bomber to level the playing field. You must make sure your using push in the halcyon to defend it. 
• It Absorptive armor with upgrades could give the radiance starbase armor of 12 and im guessing in rebellion it as high as 14 or 15.
• Its usually at armor 8 or 9 by late mid-game with absorptive armor
• Opens well with an halcyon for early game survival.

Cons:

• Anti-matter dependent.
• Animosity is the last ability to use and only works well after the 12 armor range along with an additional capital ship: Rapture with Vengeance
• Has no answer to deal with enemy halcyon carriers. 

Fleet:

• Opener: Halcyon then Radiance,
• Frigates: Majority-->Defense Vessels then Illums then Repulse(guardians) then Domina(in rebellion)

2 halcyons start is always better simply because you have bombers and 3 incredible abilities with each carrier. 

I don't know Riddle, i've noticed going 2 halcyon now is very hard to pull off because of the resources that could of gone into making corvettes is being sent on one giant ship.

I'm pretty sure I've already seen an artifact that gives more tactical slots

I like the idea to a taunt that can be targeted. That is probably the best one so far for radiance upgrade.

I forgot that there was one artifact for tax and pop growth already but I never saw an artifact that added logistic or tactical slot to all planets. Localized on a planet yes but not global. Although having an extra slot enough for a structure that takes 4 pop (whether logistic or tactical) might make it OP. 

I think my problem right now is Advent econ. They are so far behind in credits per sec that it is not even funny. They just need something to help them keep up.