My main league is entering it's 5th year of IDP scoring, and I've been loving it and am probably the main proponent for it. Like you proposed, my league began with a single IDP Flex position and we steadily grew to now having a DL, LB, DB & IDP Flex positions on our team (We use Sleeper which doesn't differentiate between DE & DT, ILB & OLB, or CB & S).

I can't recall our initial scoring settings when it was a singular IDP flex position, however I recall that during both our first season with the single IDP & our second year with 4 IDP positions, we had to have emergency league meetings to change the scoring system because there were players racking up 30-50 points a week. Again, we use Sleeper, so some of these options may not be available for you. Currently our IDP Scoring format is as follows:

•IDP TD=6

•Sack=6

•Hit on QB=0.2

•Tackle=0

•Solo Tackle=1

•Assisted Tackle=0.5

•Tackle For Loss=1

•Blocked Punt, PAT or FG=5

•Interception=6

•Int Return Yards= 1 point every 10 yards

•Forced Fumble=3

•Fumble Recovery=(+0.10 per yard)

•Safety=6

•Pass Defended=3

•10+ Tackle Bonus=3

•2+ Sack Bonus=3

Looking at it now, there are a couple changes I'd like to make, but right now it's weighted to provide an equal opportunity to each of the 3 sections of the defense.