It would be awesome to have a mod that adds a worldtype between Default and Amplified, which scales Amplified to be less extreme, so that mountains and forests don't hit the world height limit.
Ideally that scaling would be customizable, but I wouldn't mind if it were just a fixed scaling factor, as long as it left like 50 blocks or so between the highest generated blocks and the world height limit.
Alternatively, the mod would just take the Amplified generator and as soon as possible (ideally early enough that no bedrock and lava layers have to be regenerated) chop off the bottom X (50?) blocks or so and shift everything down accordingly, then continue with the Amplified world generation.
Personally, I'd love it if it were a 1.15.2/Fabric mod.