1. Get rid of the insanely-too-good all-day-effect "elixirs" 2. Require party members to be next to each other in combat to send items to each other 3. Enforce the "one spell per turn" (with "bonus action spell slot spell + full action cantrip" as the only exception) 4. Allow swapping weapons for free once per comment but make it take a bonus action subsequently (not strictly 5E rules but I think in the best spirit of them) 5. Long rest restores all HP but only up to half hit dice (as in 5E rules) 6. Restrict teleport-to-camp to specific "safe" areas with obvious clear exit routes (I like the teleportation circle idea from @arion!)
Some other more-strict-5E things would help too (scrolls for just your own class's spells!)
