The workaround against both options is to simply split the stake to different accounts.

No, it's not. See A splitting stake to A1 and A2 in my article. He can maximize usage of his stake, but still unable to take all the seats.

Limiting the number of blockproducers that a stakeholder can determine has other tradeoffs so it's a complex problem.

If you can point out these tradeoffs. I can't see any. 1 SP = 1 vote simply allows for better decentralisation. JS made an educated decision about 20 candidates, but the average person would not :)