I think the Senton and Granite Megas are going to go the way of the Dodo. The Mega series in stock form just isn't worth $230 and poor Curvin paid even more due to living in Australia. In the US you can get a brushless version with a much better driveline for $70 more. You would be hard pressed to convert the Mega to a brushless version for $70. You would have to use bargain basement electronics and you're still not going to get it done.
The biggest problems with the series is the motor and servo. Everything else is fine for BRUSHED power. I am not sure why Arrma designed the Mega with no real path to 3s. Maybe they thought it would hurt sales of their planned brushless version. I bought the Granite first and ran the brushed motor for 1 or 2 days. It didn't fail, but it was just too slow. I went to a Castle SW4/1405-4600Kv combo and ran on 2s problem free. Any breakages were due to driving. When I tried 3s I stripped the spur and that's when I decided to go with the 32p mod. When I bought my Senton I didn't even run it with the brushed motor. Out it came and in went the 4600Kv I had in my Granite (I put a 3800 Kv in it). I also put in the 32p gears. I beat the hell out of the trucks and they have held up. 4s has been tearing up wheel driveshafts but I can't blame the truck for that (not even the new truck is designed for 4s).
I have enjoyed my experience with the Mega's even though I have spent a ton of money on them. I could have bought an Outcast for what I spend on my Granite alone. But I learned a lot. I LOVE the new BLX version. They addressed everything they needed to address with the Mega and delivered it at a very reasonable price. If I wasn't so emotionaly attached to my original Granite I probably wouldn't even drive it. And the Senton? I am not a fan of SCT's I will probably use the chassis and build a Big Rock when they become available
As for poor Curvin, I would throw in the towel. The fact that parts are nearly impossible to get makes it a very difficult truck to run. Every RC breaks at some point and if you can't get parts without being bent over a barrel, then it's time to get something else.
I mostly agree with your assessment of the Mega, but I'd also throw the ESC in to the list of basic problems. Maybe that ESC works fine in the 2wd Mega line, but it is not up to par for a 4wd truck. Seems like close to half of us could not get to LVC without it overheating and shutting down. For the motor - power is fine for a brushed truck, but if you are lucky enough to get a ESc that will last to LVC, the fact that they spec'ed BUSHINGS instead of bearings means the motor cannot last a dozen runs before the tail-shaft bushing wears and destroys stuff. And yeah, a 5kg, plastic gear servo on a 1/10 MT is asking for problems. How mine is still living, I don't know... LOL
So for the Mega 4x4, you have to plan on Motor, ESC, Servo, if you want to run more than a dozen or so packs. The sad part (to me) for Arrma, at the OEM level, this is a total of about $5-$15 per truck. For us users, it is closer to $50-$75.