I like variant ability checks and agree with others that: if they're added as additional dialogue options (or you can freely select which ability score is used), then they need to have different DCs or outcomes. Otherwise, there'd be no point to using the skill you have a lower bonus in and we've effectively just decreased the DCs of checks by 0-4.
Being able to choose which ability score you use is probably too much - it'd require Larian to code 6 DCs/outcomes for every single check. So this should be limited to certain situations with handcrafted options of ability scores and outcomes.
Alternatively, I'd be happy if BG3 simply had certain situations where variant ability checks are the only option. E.g., Dexterity (Animal Handling) checks to react to Kagha's snake in the instant before it strikes or Wisdom (Religion) to intuit information about a local pagan religious practice that doesn't involve any known god/goddess.
