|David knott 242|
Working back from the Noble Scion prestige class, you want your base class to be either a skill monkey or a warrior type, but definitely not a dedicated spellcaster. That prestige class grants plenty of skill points (6 + Int mod) as well as combat ability (+7 BAB over 10 levels, with an additional +2 from your Dilettante Studies class feature), but it does not advance your prior spellcasting level very well (maximum of +2 caster levels over 10 levels from your Dilettante Studies class feature). Investigator is a fine choice for the base class, especially if you focus more on skills than alchemical extracts.
Since your effective level for extracts will never get very high, you can get away with a slightly above average intelligence but will want a very high charisma to take advantage of your increased maximum cohort level from Greater Leadership. Since the cohort you get at 7th character level (Noble Scion 2) is only one level behind your main character, you will want to consider carefully what you want to do with what is effectively a second character.