Where did I say I wanted to change the offense? We currently run a variation of a spread offense that requires a quarterback to be a good runner. It sounds like you want to sacrifice that for... what, exactly?
Comparing their first 4 seasons, Adrian Martinez was actually a better PASSER than Kenny Pickett. Martinez had a better completion percentage, and he had more yards on fewer attempts. They had a similar TD-to-INT ratio.
Pickett:
711/1177 (60.4%), 7984yds, 39 TD, 25 INT
Martinez:
670/1055 (63.5%), 8495yds, 45 TD, 30 INT
On top of that, Martinez had nearly 2300 yards rushing and 35 TDs, compared to Pickett's 568 yards and 15 TDs.
It wasn't until Pickett's 5th season that he finally broke through as a passer. Prior to that, he was less effective (statistically) than the type of guy you don't want to have at Nebraska.