If you're so tight for capital you're worried about "purchasing power," you have deeper issues than IB's capping rules. Anyway, forget "second platform, API..." and just open an account with enough capital to accommodate the odd point/click risk-control trade if/when you're prevented from executing at IB, for whatever reason -- technical or policy based. It's just common sense. What would you do if IB were down for several hours or days?
If there is somebody who would be able to suggest an alternative to IB, I would like to know. There simply isn't. We just have to accept it.
you can use anyone as a backup. most won't want to have the same buying power just sitting around, but just about anyone would do.
Little help here -- is 'drownpruf' one of Prof's aliases, or one of Atty's? I can't keep the multi-alias trolls straight...