HMEs are worse than PrimaDonnas. The latter are both annoying and not worth the trouble. Seat them near the doors, so the next strong wind will blow them out.
HMEs are simultaneously so valuable and so annoying that you must add their minor, chronic felonies to your RiskManagement insurance system. Their weekly 5 minutes of unearthly brilliance are worth more than an entire team of engineers, and in the end they cost less.
Thus make them consultants, so they must carry their own liability insurance?
it's not _that_kind_ of "insurance"!
See Also: ProjectSabotagePatterns