Arstal's comment was along the lines I was thinking of, after reading again through the posts, and the 'doubling up of tech point's' comments throughout. It's almost as if the Z factor starts at 2, then jumps to 4, 8, 16, etc.
Is there a possibility it would work more effectively (and almost practically unnoticeable until the end stages of massive map games), if the z factor started off as a fraction, then worked up on a gradual curved scale? IE: starts off at 0.01 and works up exponentially to 1, or whatever figures balance out the gameplay? This might then shove the larger tech increase amounts to the larger maps at the end, and leave the smaller maps playable on the same exponential logarithm, without having to adjust all the current base tech points?
Or have the team already considered this and gone, 'great idea in theory, but just doesn't work / absolutely nukes a hundred other things in the balance'?
Also, include an option to turn the tech increases off/on on the game start. Allows those who just want to play with base tech points, do so.