Scenario 1 - dictionaries everywhere, put dictionaries into containers with objects, then you can definite as many bits of data as required. Or just use instance variables. Then lots of comparisons for whatever is needed.
Scenario 2 - have a dictionary for each player called "attribute overrides" that always contains an up-to-date list of equipment buffs and such (if changing equipment, refresh this dictionary) so could contain keys like "Jumpstrength = 2" for a 200% increase. Then, have vars in the player such as accelspeed, jumpstrength, hpmax, attack speed. Then have a custom action, or function, that does a sort of "refresh attributes" system, where it starts off by setting the attributes back to the overall "default" value (E.g. Jumpstrength gets set to 300), then throughout the custom action, multiply the attribute by whatever keys it can see, depending on the key name (so the players variable "Jumpstrength" which is currently at 300,gets multiplied by the Jumpstrength key in the players own "attribute override", meaning it gets increased 200% and ends up at 600).
EDIT: Your video where it would judge speed of work flow and such, I don't know much about making videos or comparisons, but if say you asked me to demonstrate these 2 solutions, then for each I'd whip it up in less than 10 mins from scratch, adding more time for each extra attribute or gem type and such, using built in behaviours and plugins (and assuming I use rectangles for artwork since I'm bad at art).
Since these are new solutions for you to think about, you might take longer with speed of workflow unless you have done these systems previously (I'm not assuming you know less or judging your competence with C3). But, if you told me to whip up an RTS with moving units and pathfinding, then I'd definitely be much more slower and unsure, whereas others would be lighting fast at this. I don't quite know what my point is but, I see event sheets as powerful and doesn't work against me, and you have titled this post as C3 being a nightmare and such, which is just baffling to me as someone very familiar with event sheets and don't often have issues with it and feels like I can get any result needed.