There are only 1.5 million SPR right now. (And 3000 * 2500 = 7500000, but that's beside the point.)
A dynamic collateral requirement just limits the number of people who can potentially run a MN. With a fixed requirement, those who wish to earn more can do so by setting up another MN, without limiting the ability of anyone else to do so.
This will lead to awful centralisation, I guarantee it.
As long as each node pays the same regardless of coins in it, then someone putting up a 10,000-coin node is no better off than the minimum node. Doesn't this solve the centralization issue?Edit: I think I get it now, someone could set up a bunch of cheap nodes to centralize the network. It does look like a minimum # of coins still has to be enforced to set one up.
By only setting the # of nodes high or low, it can be gamed by a nefarious actor.