That's a very good question.
As long as people with disabilities who are accessing these two credits are not worse off as a result of a very well-intended tax cut, I'm not particularly wedded to any method of doing so. I think that making sure it stands the test of time is the thing we're most concerned about. We don't have to go through this all over again with any subsequent tax cuts.
Altering the method by which the DTC is calculated is probably the best way to go in order to make sure there aren't any further issues. Proactivity is a nice thing.