I don't know if this is a good idea or not, but it's an idea, and I'd like to know what you think.
Imagine a d20-based RPG where the numbers you add to the d20 roll generally do not improve as you gain levels, and this goes for monsters as well. There's no proficiency bonus or base attack bonus that increases with level. You still gain new abilities, spells, with levels.
The system has something similar to advantage and disadvantage, but you can gain more than 1 die, depending on circumstances.
When you attack a creature lower level than you, you gain an advantage die. When you attack a creature higher level than you, you gain a disadvantage die. Something similar happens with saves and perhaps skill checks.
If the level difference is large enough, an additional advantage or disadvantage die is gained.
Possible positives and negatives of such a system:
- Easier to manage character sheet and progression.
- DCs don't have to "artificially" increase as PCs gain levels.
- Players can tell whether a creature they attack or are attacked by is higher or lower level based on extra dice awarded by the GM.
- Might feel like there's no progression from looking a the character sheet. (Mostly the only numbers increasing are HP and level)
- Less granular difference between creatures depending on level difference.
- GM must award adv/disadv more frequently. Might slow down the game a little.