Once I have abandoned my copyright and placed the work in the public domain, you can do anything you like. You could even put a copyright notice on it claiming it is your own copyright (but good luck enforcing that)
Where is this coming from, Daphne? Are you sure that this is a licensing issue? SRFI has used the MIT license successfully for well over a decade now, and it has not been a problem. Is it really that important to you? Licensing issues truly are not what gets in the way of adoption of SRFIs.