I imagine the implementation would be quite difficult, and the responsibility of board designers to use them and make maps that don't suck would be high/hard to meet, but...

I would like to see conditional board elements added as a map feature. As in, continents that only give their bonus if some other condition is met. Perhaps, for example, some continents only apply to Seat 1 and others only apply to Seat 2. Or, borders that only exist when someone occupies a "switch" territory or completes a continent to, for examples, lower a drawbridge or open a gate. Same with border modifiers. The possibilities are really pretty endless as to what you could make your 'ifs' and what could be your 'thens'. But if you picked a handful for each element, I know I could really add some cool ideas to games.

Other possibility is continent bonus values that increase as the number of players on the map decreases. Give me this feature over cards any day.

I love the idea of borders appearing or disappearing... you're right, it would be very tricky to do. We'd have to develop some sort of interpreted board language that would define the game logic and then the Player / game engine would run through the logic each turn to modify the board structure. Definitely doable but definitely hard!

re: the continent bonus modifier - that could be quite easy to implement if it was just a straight multiple - e.g. new_bonus = (x - num_players) * original bonus. You would just define value x. What else would you need to define if anything?

straight multiple ought to do it, as long as you let us make the multiple a fraction or a negative, too. bonuses don't necessarily have to grow, maybe they shrink. maybe they shift around.