HQ Deathmatch Help

So following the success of my Dreadknight I want to win all the deathmatch types for the Grey Knights. Problem is I'm stuck for a HQ. My original plan was just to take Draigo, at T5 4W 3++ and Eternal Warrior the guy is pretty beastly. However in the last Deathmatch the nastiest character imo was the Necron Overlord kitted out with all the upgrades(even if he did lose to Abaddon in the final) and that made me consider taking a custom GM with all the trimmings. However I've not used 90% of the cool stuff in the dex since I tend to take a libby rather than a GM, so what I'm looking for is some opinions on the following build and some probably obvious answers on some wargear and stuff.
First up my GM
Mastery 2
MC Stave
MC Psycannon
Digital Weapons
Brain Mines
Rad/psykotroke/blind grenades
So how do you guys think this would stack up compared to Draigo? Obviously the lack of Eternal Warrior is the biggy, there's the potential to get splatted, last time there was Abaddon and Logan Grimnar with Str8 CC and the Necron Tachyon Arrow being a str 10 shot. I'm kind of gambling on the 2++ (4++ for the arrow) being enough to keep me alive and the effects of the various nades being useful enough to neuter my opponent for the first round. I think if i can get initiative the psycannon followed by the grenade/beatstick combo I might be able to do some serious damage. I have to say I'm quite looking forward to going against the Necron guy with a potential slew of effects considering he had a nasty combo of using mindshackle scarabs to make people wound themselves and then using the tesseract labrynth to finish them off(the reason he lost the tourney was Abaddon somehow passed two 3D6 LD tests in a row in the final). So onto some questions I came up with(I have far too much time to think while ill lol)
1)If we get locked in combat do brain mines work in subsequent rounds?
2)What happens if I roll a 6 for psykotroke nades and reroll another 6?
3)If I use Draigo and face the Necron and fail the mindshackle test do I hit myself at str 10, I'm thinking yes
Also as an outside shot instead of Draigo or the GM are there any other options people think I should try for a lugh? I'm thinking either Mordrak for the surprise! ghost knights or the Brotherhood Champ for the rapier strike / heroic sacrifice combo, although what that would do to the tourney I don't know since we'd both (hopefully) be dead.

I'd still go with the customized GM. Depending on the results of your grenades, you'll do a lot of damage even if the guy is immune to ID. Just hope you don't fail your 2++ saves vs. ID attacks.
1) As I understand it, yes you can use brain mines in subsequent assault phases.
2) Rolling a 6 for psychostroke doesn't require you to re-roll.
3) Yes, I agree, Draigo will probably whack himself at S10.

too bad the Brotherhood Champion only has 1 PV, cause he would be a good choice for those type of games, he's very resilient and hard to kill. And if he dies, you can probably get the draw !!
i would probably go with him, just to see how this "little" character can match the other über HQ... if not i would probably go with a customised GM too as brother Rivan, with the 'nades of course !
Aubec

Thanks for the advice Brothers, will be interesting to see what happens when I start throwing 'nades everywhere.
@Aubec The BChamp is a decent HQ killer with 2+ 3++ in CC, and Heroic Sacrificing everything sounds fun, but I'm worried my store will just arbitrarily rule it a loss since he goes down first or something which would suck, although to be fair if they don;t we could be there forever lol