Can you make it track something like the average amount of interups per key on party members? Or maybe average use of defensive spells. Nowadays it's hard to tell if a high io is a good sign since people can buy those things

Like keeping track of it and saving it so you can see this info in things like tooltip or something throughout the season or just per run ?

Should we still do this ?
We would need a Webspace and then I could build a website for this
(I know a hosting service that has pretty good Lifetime deals (5GB 46€, 10GB 58€, 20GB 82€))
And then either put the upload / download data thing into an App or make it available through the Website
This could be done like Raider.io but with just M+ Related statistics through logs

It sounds to me like this person wants to have this data on people to decide whether it's worth doing a run with them or not. This would require aggregating data from players and storing it on some central server, which then also necessitates a desktop client to sync that data. That's an operation on the scale of raider.io and something I don't think we should want.

i mean if we're doing it on a small scale then we could push the info through addon updates instead of having a client or just let the user download data manually from a web server

Yes we should build a complementing website to see m+ stats