It starts with reigning in the bonuses. I'm not a fan of expertise doubling your proficiency modifier, for example. I also adjust most of the DCs up by 5 points from what's been published.
We have three levels of proficiency that is consistent across all types of proficiency (skills, attacks, saves, etc.), although there are a number of things (weapons for example) that expertise is currently not available. I'm still considering what the impact of that would be.
Non-proficient: +/- ability modifier with disadvantage
Proficient: +proficiency modifier +/- ability modifier
Expertise: +proficiency modifier +/- ability modifier with advantage
We've also considered (and are very close to doing so), granting everybody proficiency in Perception and/or removing it as a skill.
Does that mean you roll with disadvantage if you are not proficient in a saving throw? That seems like a pretty big impact on balance when non proficient characters try to dodge AoE damage for example.
Also, why did you up the DCs by 5 points?
Say some character is not proficient in persuasion. Rolling with disadvantage means that character could only succeed at a very easy task like persuading a child to eat some candy (normally DC5, now DC10) with a chance of about 30%.
What is your reasoning behind removing perception as a skill?
Have you figured out how to handle weapon expertise yet?
Thanks for considering my questions. I like the idea of your approach, that's why I am asking.