1) What about
Light Tank -> Tank -> Battle tank
2) In this way you would leave romans with no armies until iron working...remember, the legions come later. I think I'll make them replace swordsmen with
3) I think I'll remove alphabet. Writing and alphabet sounds the same. If you know alphabet, you know how to write!
About the gov's, let's postpone the problem.
4) If I postpone Astronomy too much, America will be discovered too late.
Otherwise........I could move caravels to magnetism and apply your changes.
Physics is going to give Newton's university.
It doesn't hurt strategical decisions, as it is the last researcheable tech
5) There are other problems:
-the last techs in the upper path must be corrected
-something must be put in the middle of the lower path to substitute Replaceable Parts
6) So, supercondutor is a future tech?

I'll move it at once!
I'll add "Mobil Warfare" at the beginning of the age, too. It will allow tanks.
7) nice idea. But there's one problem: when the wonder expires, the upkeep remains....afaik wonders can't be sold.