In regards to drawing mana from the land, what if: As you enter a hexagon, a mana bar for that region begins to increase based on your experience in that element and the strength of the mana present. The longer you are there, the more mana you tap. Upon leaving the hexagon, that mana bar begins to depleate based on your experience and on your distance from the hexagon. The mana coud decrease logrithmicly (you lose a percentage of your remaining mana every time unit, so the less mana you have, the slower it disipates) so that you only lose the majority of the element-specific mana to begin with and you only lose it all if you spend it or spend too much time away from that element.

What do you think?

Just another point to ponder, how complex can you make this system before it scares people off?