Having larger nations being player controlled may make for a shorter session, however having stronger player nations from the start would foster more early and complex alliance webs to counter balance this. Having everyone playing weaker nations just extends the same problem to a later date, as players will have more time to focus on gobbling up small AI nations before being forced into PvP. Our main problem is that when alliances form, they generally last forever, instead of shifting to counter a powerful nation, and thus keep the game rolling for longer.
Anyway, in lieu of a better idea that I don't have, raising the rank limit for a bigger range is agreeable for me, though we should either go to 10, or stick to 5 but use non integer values when rating, e.g:
France - 10, England - 9
or
France - 5, England 4.5
Both will have an increase in range and accuracy over the current model.