I actually made a suggestion about a bigger battlefield: Suggestion: Increase the battle field size - Discussions and Feedback - Ikariam (gameforge.com)
3 months ago.
And i agree, we should have a much bigger battlefield than our current situation, but if this has to be done there should be some balances too.
Number 1: And the most obvious is more / higher levels to the walls. Cause otherwise a bigger field = the defender would loose in fewer rounds
Number 2: More upgrades to units for attack, health, defence and accuracy, ammo capacity, less troops space on field (So more units can be placed).