Hulking Lummox
Warlord
NO no no no no. Absolutely NOT.
By doing that, you ensure that the tech leader of the Ancient Era gets an insurmountable advantage for the rest of the game. The first person to reach the Ancient Era WILL be the first one to reach the Medieval era, and so on so forth. He will also effectively deny any other civ the ability to progress at a reasonable pace, thus locking everyone else out of all victory conditions, except possibly domination. And gods help the world if the tech leader beelines military technologies...
"And I hold no attachment to the "exactitude" of my idea so it could easily be tweaked around." - from my post. I speak more from a place that ideas can be collaborated on, not Pass/Fail.
The hypothetical first person into the next era didn't receive a free tech, they got to sit on the tech like the king of the hill. The difference from the game at present is that the first person to the next era actually had to WAIT to move forward. Instead at present you would have blurted "HOLY S**** as Hiawatha entered the Atomic Era while you're way in the way back. Also there is no guarantee that someone who was teching in a more balanced way won't take the lead on the other side of the tree. Also, it's just a suggestion. Nothing is being imposed on anyone via my forum post. I operate from this place - that personally I never make any suggestion without assuming it would or could be balanced by the development team behind the game.
As for getting locked out and someone else getting an advantage because they were faster, lets think where else that happens in the game... Wonders, Ancient Ruins, City-State Quests and Alliances, Pantheons, Religions, City Placement, and so on. A big part of what I am proposing is that the tech progression of the game be made interesting by making "discover a tech" with a GS worth using in the first 75% of the game (worth using if you're still planning to go for a tech victory that is). I'm not sure you properly envisioned the idea of more GS's being in the game, which I did mention. Artists have gotten their overhaul for BNW, maybe there can be tweaks to GS's in the future.
If I know someone is the techleader and they entered the Renaissance via banking, I might choose to use a GS to grab Printing Press even though I'm locked out so that I can start building the Leaning Tower. What I'm putting out there doesn't even have to be a hard lockout against the other civs, maybe it could be based on a mathematical total of what the other civs have researched in relationship to the tech leader. Or maybe you just can't BE two eras ahead, period. Whatever makes for better for balance than what we get now with the B-Lining AI who is still allowed to grow ridiculously even though they probably didn't grab fertilizer or something.
The focus is on holding back ridiculous tech runaways so that factors within any given era can come into play. For example, a really streamlined version of history: Forward progress slows while Germany is in a tech lead in WWII (but the US uses some GS's to discover atomic theory). You just need to imagine the game differently.
Could it be perfectly implemented with all factors in the game happening at the current rates that they do (with Victory Conditions in mind)? Absolutely not. But could it be a significant way to overhaul the tech game and still have it be interesting? I think so.