What we need is as much bandwidth as possible. But we also need this bandwidth to be distributed to as many peers as possible in order to be less dependent on single forgers.

Your idea of diminishing return for multiple Nxt on the same IP is one way to reach that goal.
But i think, that each Nxt should have the same forging power. Everything else will result in people feeling betrayed. Also it might be possible to game such a system.

My solution does not garuantee high and distributed bandwidth. But it gives incentive to forge even for smaller balances (of course only possible with fractional NXT).


Of course it is impossible to forbid pooling. But if the protocol would distribute rewards more evenly, they would become obsolete..