Maybe there should be an extensive discussion on here how exactly that would look. I think it is realistic that we see a single-age mode in which all techs and civs are copied into antiquity, but this comes with many problems that need to be solved (resource generation and unlock/lock of mechanics and buildings, for example). If the CFC community could get behind 2 or 3 possible ways to tackle a classic mode in its entirety, that might be informative for a future rework. Not at all an easy task, especially as everybody has different preferences, but it might be more interesting and worthwhile than hoping that FXS will do it one day in their way and it will somehow be awesome from the start.
Some time ago I was thinking, how to solve problems, which Civ7 solved, while avoiding controversial features. The result was far from perfect and it definetely was impossible to make it at Civ7 expansion. I really think Civ7 will stay as it is, but as a mental exercise:
To solve the problem with late vs. early civ bonuses, the game need to move away from unique units and buildings (there still could be civilization specific visuals) toward unique bonuses. Unique improvements could stay as long as they are available from early game. By unique bonuses I mean something which affects, for example, all melee units regardless of their epoch.
To solve the problem with game pacing, I thought the concept of legacy paths or similar quests is more important than the ages themselves. So similar big quests (build X wonders, etc.) should still pop up and contribute to victory.
Distant lands are a decent idea, but their effect on map generation is devastating. I'd keep continents concept from Civ6/7 and make continent-specific resources which you could grab either through settling/conquering on other continents or through intercontinental trade, which could more difficult than regular trade to discourage turtling on home continent.
Balanced land in Civ7 is actually ok to me. Randomness still come from resources and not having trash starts sound good even for SP.
For MP, I'd make some scenarios which are as close to normal game as possible, but limited in time, similar to Civ7 ages. Probably built them on top of legacy path mechanics and modify map generation for more balanced play. Thinking of this, current Civ7 ages taken separately (I assume they'll come that way in the next patch) should be very close to MP-focused scenarios in this hypothetical game.
Finally, to battle snowball effect, some additional game mechanics need to be introduced. But instead of resetting progress for all, I'd push it for those who are behind. I.e. once any player discover rifles, all melee units for all civs are automatically upgraded to early gunpowder. Something like this.
