I actually got to make a nice list with potential changes, but sadly the release of TfV and work on other projects kept us busy and we never got past that very first stage.
However, what I can offer you is one of the things that I wanted and that was easily scriptable (mostly because it is already part of my DBZ mod): Synergy Inventions.
There is one for each tier in each tech category and it is activated by researching every tech of that specific tier within that category (e.g. all tier IV Culture techs). Synergy Inventions have a (+) at the end of their name to distinguish them from regular inventions.
Each Synergy Invention gives a small bonus geared towards that specific tier's timeframe. Should make some of the weaker techs more desireable and incentivise players from NOT completely ignoring some of the Commerce or Naval techs.
I'll attach the little thing as a mod below. Put it in your V2 mod folder, activate it via the game launcher and enjoy.
Not save game compatible! English localisation only!
Merry Christmas - and long live the queen!
https://forum.paradoxplaza.com/forum/index.php?attachments/xmas-rar.226712/