If you uninstall the ipv6 and/or wireless package first, it may free up enough space for the upgrade to be successful.
Actually this worked...
And after that I simply restored binary backup (which I made prior), to get wireless and ipv6 config back.
Also since RouterOS v7 beta was first released back in September 2019 it has been known that the ability to install the individual packages (system, wireless, dhcp, etc) is gone and everything is in one monolithic package, only making upgrades easy from the v6 bundle package, unless the device has a lot of free space. If you set up your hap ac2 two years ago, that was after it was common knowledge that MikroTik was doing this with v7.
I don't remeber exactly when I actually did it (they are fairly old), what I do remember, I did it before first v7 public betas appeared and first day I got these before putting into use.
Anyway, apaprently I found a way, which would work and I also mentioned it here, so if anybody else runs into the same issue, would know it as well.
Thank you everybody for your contribution, would have not been able to do it that smoothly without you.