I'll suggest a different approach than naming potential names (previous post - and I forgot Jay Johnson, former runner and assistant if I remember correctly).
What does CU need/want in terms of recruiting and coaching approaches?
Recruiting - CU recruits itself as a university AND as a XC program (not track so much; at least the non distance events). So... you don't necessarily need a grinder recruiter, but you need either
(a) a flashy name (think Prime Time transfer central)
or (b) a person with significant credentials to win the end of the recruiting battle.
Coaching - If you go with (a) then that person needs to be surrounded by other coaches who KNOW how to coach / develop - if that person doesn't possess those skills.
If you go with (b) - that person likely has those coaching/developing credentials for a reason; and in that instance, they may want to surround themself with a flashy assistant who can attract the attention of recruits and buy into the coaching system/philosophy.
Intangibles - Associated vs not associated with previous/current CU program
One advantage in going with someone on the inside is their institutional knowledge of how things have been done. They've seen how successes come from their approach and could conceivably continue those efforts.
The investigation, however, may warrant looking OUTSIDE those currently or formerly associated with the program, to put distance between connections and the investigation.
Perhaps CU Admin would blend both approaches - someone new for a "fresh" look coupled with key positions of those continuing the tradition?
Of course, that could also work with Mark staying on (continuity) while hiring an outsider with a fresh look on the program.
Whatever direction they go, CU will have A LOT of viable options.