Terrible idea? Sure. But I've always had a soft spot for terrible characters. I've liked emphasizing on RP more than hack and slash. If it really is such a bad idea, the DM can ban those if they deem them inappropriate for a "high risk fantasy" game.
I've never even heard of that before, so I can consider it.. though it honestly doesn't seem like too great of a difference to bother with, and will make costs even more complex.
The one part where I strongly disagree with you. I've had some experience building characters in M&M, and I found that the "optimal" way some build characters is to completely forgo all other stats, but just max out CON. Because it gave so many benefits at the most economical cost.
When you do the math, with d6 hit die being normal, then a d8 hit die on average yields you one more HP per level, with the incremental costs. As you level more, you get more HP, but you pay more. Constitution, on the other hand, with just a flat cost.. you pay once, and the more you level up, the more exponential it pays off. This is in addition to your fortitude saves, plus any other class features it may improve later. A smart munchkin will just pick the d4 or d2 hit die and then just massively pump their CON to get their HP.
See the disparity in the math yourself. Without the incremental cost to CON, getting 18 con costs 16 character points. At level 20, for instance, you would have boosted your HP by 80 for just 16 CP. But if you chose to get the largest hit dice of d12, you'd only be increasing your HP by 60 for the cool price of 60 CP. Given that scenario, who in their right mind would ever do the latter?? And yet, to cheapen the cost of increasing your hit die would seem to make it way too easy to inflate your HP. The only logical option was to nerf CON.
And do you think wizard spells will be free? I'll give you a little hint of what's to come: wizard spellcasting will have large incremental costs that put these "chassis costs" on par with each other.
I don't know what you mean. It's a flat out lie that skills do not have anything to do with fighting monsters or lack importance. Same thing with base stats.