Which is why the mechanic should reward a solid, historical game. Some ideas:
1. Periphery penalties scale by era as well, to where they are equivalent to as they are now in the modern era. This helps to resemble the old expansion civics - you are able to do more outside of going straight down the historical path as the game progresses. Call the current penalty for not being in historical or contested area 2
. Proportional to this, the penalty scales approximately:
Ancient - 12
Classical - 8
Medieval - 6
Renaissance - 4
Industrial - 3
Modern/Future - 2
Which translates to: don't try to pull anything interesting until you are somewhat established. The classical penalty is not much of a problem for Rome or Greece since their UHV areas are historical territory. Lower penalties in the later eras
2. Make steel a renaissance tech. This does not relate directly to the problem, but it is on line with Steam Power, which is one.
3. Worse and more certain results from bad stability. In the past, I had talked about some sort of critical turn limit to how long one could go with bad stability and not collapse. Here is another that goes along with (1) and might also discourage beelining: each era transition (and/or certain technologies) has a stability number associated with it that one must be above in order not to collapse to core. As well as discouraging early foreign area expansion, it also simulates better those empires that have their distinct eras, and then become irrelevant without directly penalizing specific civilizations.
4. Nerf coast tiles. If one looks at youtien's Straight English or if he were to post his core from the above Spanish game, one sees that he is getting a lot of his population from 2 food coastal tiles. Either subtract the number of worked coastal tiles from population when doing the modifiers or do something to harbors, like make it such that only fishing and whaling boats provide additional food, not every single tile.