Proven airframe, fuel efficient turbofan engine, huge capacity (up to 30x500 lb bombs) and/or long loiter. Better CAS platform than modern fast movers, yet has plenty of capability for 90% of missions flown by the USAF and Navy/Marine aviation over last 25 years.
Yes this would be admitting that we don't need to spend a Trillion on the F35, and $35-$50k per flight hour for milk runs.
Obviously I'm talking about giving the craft a glass pit, modern sensor pack and updated engine, maybe even a back seat too.
I'm really also addressing the huuuuge gap between desired capability and actual use-case for at least a portion of our airpower expenditures.