When the committee considers proposals, we do consider the implementation burden of the proposal as part of the feature. If parts of the proposal would be an undue burden for an implementation, the committee may request modifications to the proposal, or justification as to why the burden is necessary.

Thanks. Do you have an example of a proposal that the committee considered an undue burden for an implementation but was otherwise sound?

Not off the top of my head, but as an example along similar lines, when talking about whether we could realistically specify twos complement integer representations for C2x, we had to determine whether this would require an implementation to emulate twos complement in order to continue to support C. Such emulation might have been too much of a burden for an implementation's users to bear for performance reasons and could have been a reason to not progress the proposal.