Back to the days I was fixing a lot of computers of friends and relatives, my Swiss army knife of Linux was https://www.system-rescue.org/

Very lightweight but with a full set of recovery tools. I’ve tried it recently and I still find it up to the expectations.

I’ve also used a fair amount of https://clonezilla.org/ to (re)store images of freshly installed OSes (mostly windows XP and 7 to give you an idea of the timeframe) for people who I know would have messed up faster.

A lot of technical aspects here, but IMHO the biggest drawback is liability. Do you offer free storage connected to internet to a group of “random tech nerds”. Do you trust all of them to use it properly? Are you really sure that none of them will store and distribute illegal stuff with it? Do you know them in person so you can forward the police to them in case they came knocking at your door?

Yes, you can do it on your server with a simple iptable rule.

I’m a little rusted, but something like this should work.

iptables -t nat -A PREROUTING -d [your IP] -p tcp --dport 11500 -j DNAT --to-destination [your IP:443]

You can find more information searching for “iptables dnat”. What you are saying here is: in the prerouting table (ie: before we decide what to do with this packet) tcp connections to my IP at the port 11500 must be forwarded to my IP at port 443.