corbtcomp.tf has been using archive.ph for this kind of thing since 2014. For example, the old i55 splash page on Insomnia's website is archived here. There's probably better apps than archive.ph out there which might be worth switching to.
I started by archiving TF2 Storylines: compLexity TF2. From there, these links could be put on the corresponding ESEA season pages on Team Fortress Liquipedia or comp.tf as external links/media.
As for comp.tf, we could go a step further and copy the text and create an comp.tf article for each ESEA article. That way if archive.ph goes down, we still have copies. Not sure if Liquipedia would allow that kind of content but hopefully they do.
Not sure if there are better solutions elsewhere, but I can start working on archiving these. Would be a big shame to lose them.
the wayback machine/internet archive is another good choice to archive stuff