I don't think we actually need any of the modes described in
newmodes to be REQUIRED. [...]
I believe the goal is "if you support 'newmodes' you must support
aes128-ctr" so that two implementations which claim to support
"newmodes" will not fail to interoperate because one only supports
3des-ctr and the other only supports aes128-ctr.
I don't see that as an especially useful property, because I don't
think "supports `newmodes'" is a useful thing. "Supports aes128-ctr
from `newmodes'", or "rekeys as recommended by `newmodes'", or the
like, those could be useful, but newmodes qua newmodes isn't so much a
thing to be supported (or not) as a convenient umbrella under which to
collect a bunch of individual things to be supported (or not).