For those wondering the need, Tezfiles commonly mirrors the same content uploaded to K2S. The links are interchangeable, however despite Tezfiles providing more than double the bandwidth speed for download and being anecdotally much more reliable as well, 99% of posted links are K2S, not Tezfiles.
This was supposed to read "How I would envisage such a script to work is the browser address line is monitored for either k2s.cc
OR keep2share.com prefixes" and not what came out above. I can't edit the original post now.
How I would envisage such a script to work is the browser address line is monitored for either https://k2s.cc OR https://keep2share.com prefixes, and immediately upon noticing either, it is replaced with https://tezfiles.com instead. The script also includes an optional button on the toolbar you can click to toggle easily and quickly between the two (in the case that the tezfiles isn't hosting a mirror of the k2s content.)
Name it k2s⇆Tez and have ⇆ as the symbol on the toolbar button to toggle between the address prefixes.