Removing vitality scaling entirely would mean reworking every damage number in the game. A lot of work. Constitution isn't that bad, just needs a slight buff, perhaps some kind of additional effect on top of vitality bonus, preferably not just another form of extending life, but like how con increased maximum AP in the original.
Con could still increase the maximum number of AP gained within one turn, perhaps, given you can get up to 8 or 10 or possibly more, with adrenaline, haste, elf racial, glass cannon, warlord, and tactical retreat. You'd start being able to gain up to 6 AP a turn (like if you had glass cannon), and every 2 or 3 points of CON you'd gain another maximum AP. This is to say, this is the maximum amount of AP you can GAIN in a turn, not have at any one time (like as now.)
This would help balance out the AP overload of these various skills, and allow further additions of +AP skills. Want to be an AP Junkie? You need to have the stamina to perform several actions in quick succession. With 2 Con to +1 AP max, you'd probably only need to invest 8-10 points for a realistic maximum AP gain, but at least that's something, especially as a limit for earlier on in the game.
