Well...
i had about the same ideas about half a year ago, just wanted (for simplicity) to make a thwackbot, not a flipper.
And it was only for the raptor class, so just 6kg and limited to 12V. Still wheels with 30cm diameter.

Encountered a few problems there (actually a few more, but will try to mention those that might matter most to you.

1. controlling.
It is really, really hard to maneuver such a thing. I had a quiet heavy "tail" to drag around, that also came in, but still... any wedge (or non-wedge, that is) bumping into you from any direction make you drive over it. Good to not actually harm you, but not good for controlled, precise driving. Look the fights of Gabriel and HUGE, they are all over the arena just smashing around anything they could reach. Not because they want, but because they are hard to control once a wheel is lifted just a bit.
Another thing is, you'll need a kinda wide stance. I had 30cm wheel diameter on a bot 28cm-ish wide. That stance was not wide enough, might have to do with the tail, too, but whenever i tried to do fast maneuvers, i flipped myself because the center of gravity was too high.

2. Landing on your sides.
You WILL need some spikes of some sort on your wheels to make you selfright when you land on your sides. Which will happen quiet often. I hoped to just spin on a wheel then, using how unbalanced the bot would be as spinner to flip myself over again. Doesn't work (or not good...). Also, While on your sides, your precious electronics would be in reach of any spinner. Might be the flipper could help on self-righting, but i don't think so, with it working sideways then...

3. rotating yourself.
As i see your design, you'll constantly rotate yourself around your axis when you try to drive forward.
That already is a problem with many flippers: front really low to the ground, but if they accelerate to charge, the front lifts up a bit. in your case... that problem will be multiplied if you want some good acceleration. You'd need something like those stabilizers on childs bikes, just to your back. Leaving you to have stabilizers in the back on the ground, flipper on the front, and the wheels in between easily loose contact to the ground. or make the stabilizers more flexible, still leaving the front to rise a bit.

4. Torque.
You mentioned it yourself...
in my setup, i used the Ranglebox Neptunes wit 18V Motors on 12V (just out of time problems and rules...), so there is more potential with a better setup. Still... even undervolting the motors that much gave me a smoking robot at the end of the last fight, burning one motor. Not because of enemy hits, but because i was on one wheel and tried to rotate the hole bot to selfright. And they got pretty hot after each fight. The wheels were slipping like hell, but there i mostly think it was the center of gravity being quiet a bit away from them, should be better on your bot. So while you possibly will have enough torque to drive yourself, you might get problems with overheating the motors, since it will be like (almost) continuous (almost) stall current through them. Don't know the gearing of the argos drills without searching, but that is something to keep in mind. Some cooling could possibly help here, too...
Anyway, that is a big possible problem, and since i did an awkward setup, you might have less problems with that. Or more, since your bot will be twice the weight, and since i used solid wheels, the percentual mass you want to move is a bit bigger, too

5. Fixing the wheels.
The usual easy method of "just hammer/melt a nut into HDPE-Wheels to make them fit on Drill shafts etc." does NOT work with such big wheels.
Had 5 fights with my bot using that method. in 3 of them the wheels came off, the other 2 were lost because i landed on my sides. Was my first bot, and i did some design errors i've seen right in the first fight but couldn't fix all of them while at the event... But this was the biggest flaw.
You will need a hub of some sort, and a good one, too.
And don't underestimate the forces on the gearbox shaft. since you can't stabilize it from the other side, but possibly jump a few times with that flipper, there will be a lot of force and leverage on the shafts. I used some 40mm square tube of Ali to push the gearboxes in (after some filing), and also push in some ali squares with fitted in ball bearings to further support the shafts. This way i had a rather sturdy construction with the shaft not only fixed in the gearbox, and it was one of the few parts actually working really good.


Besides that, it is really fun to drive such a thing, and it is something not so common as the usual box/wedge-shape.
Don't know about the flipper part, but i did my simple thwackbot including design and stuff within one week on evenings/night with nothing more than a jigsaw, a cordless drill and a file (and ordering a few things^^).