It's something I started doing last year.
Right now the Lions and Chargers each have offensive lines where the average starter age is ~26 years old, and they each have multiple pro-bowlers and/or All-Pro/Rookie team members. Teams like that have long-term potential to keep a good cohesive unit together for a relatively cheap price.
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.