well there is 1 little thing that you haven't thought of. People with lots of rares and score could simply give away loads of electrum and rares, for example several people got over 1M electrum they don't have any use for. This means we coudl end up with noobs that got 100K electrum and all rares, making bronze extremely hard etc etc.
I did think of that and basically just don't care. We already have that - there are plenty of alts in bronze already with a ridiculous amount of wealth. Additionally, FG grinding with low win rate stuff like firecell already creates situations where new accounts have high wealth but low score. Those looking to give away wealth can already just set up pvp farms in the communities where it's allowed.
All people need to do to have high powered bronze accounts is to burn score off when they level up out of bronze. This is already happening (and has been happening for years) and hasn't destroyed bronze. In my personal experience it's generally less of a good idea to spend your limited skill points in bronze on upped cards than on HP, which is why you don't generally see a bunch of upped decks in bronze.
The only bar we really need to cross on this is "less exploitable than pvp farms" in order to guarantee we don't negatively impact arenas, metas, etc. by providing some new exploit to the people looking to exploit.
As a side conversation: is there any system that you (or anyone else) can think of that would allow people the ability to provide prizes for unofficial tournaments/etc that would be less exploitable than this? There is great value in providing such an ability, and not providing that ability encourages people who want to do such a thing to not participate in this community and instead go to places where pvp farming is accepted.