Advice needed: how to upgrade TAZ 2?

I own a TAZ 2 since 2014-2015 and would like to know if it is possible to upgrade it. I see in the upgrades post that one should at least upgrade to TAZ 3 to use some of them…

So, where to start? How to upgrade TAZ2 to TAZ3?
The only thing I can think of now is upgrading the firmware. But any other options?

I installed Taz 5 style leadscrews, E3D V6, PEI sheet on the bed and the openbuilds upgrades on X and Y. That is all it needed. It is still the most reliable printer out of all I have.