Don't think it will be a major problem, given that most systems these
days have a DVD drive ( even if it's only DVD ROM ) and/or can boot
from USB. Hardware that's too old for that will also probably be too
old to run the later Ubuntu any way, or at least not run it well

Easy enough to keep an ISO of older Ubuntu versions and a CD of them
for those systems that need it - more as a repair tool than install
Ubuntu onto them.