1 would change a lot about how the game is played, neutral, etc. A lot of the issue on air dodges is invincibility but spot dodges are still worse than Brawl and it's probably the length of rolls and their low frame data that is the problem, not their invincibility.
1.) Reduce 25% invincibility (not total frames) on rolls, spotdodge and airdodge.
2.) Reduce shield regeneration to 50% of it's current state.