Reduce the turn timer to 15 seconds
If someone can't play out their turn in 15 seconds or less, then they don't know how to play their deck and shouldn't be playing it.

-
CrispyChestnuts#09605 commented
How then do you propose they learn how to play their deck against humans or anything at all but sparky and sparky's 5 decks? Don't they by definition need to play against people to learn how to play against people (unless arena upgrades sparky by quite a bit someday)? we can't assume they have access to any additional resources, like a LGS, paper cards (esp because arena has cards that will never be printed), or a MTGO library, so solutions that are agnostic to people's resources would involve IP theft (like proxy cards or 3rd party software or something)