I'm not sure that works. But perhaps I'm missing something.

If you half the collateral, it doesn't follow that you double the masternodes.

First, the block reward hasn't changed, so the revenue to run nodes remains the same overall.

Second, going from one MN to two would potentially double the cost to run them - you have to ignore any speculation on price increases, although it would (speculating) potentially go up with real world adoption.

So, one server goes to two servers, but the reward remains the same.

If you introduce a micro fee, that would enable the network to scale with a reduction in collateral requirement.