One - now successfully retired - Angel Investor I know had two rules for investingin startups:
this guy was an old Quantum Mechanics grad so his answer when asked "why" was "I don't need a why when I have as long an empirical track record as I do. If you pushed him he would speculate that MBAs are tought a way to "MANAGE" a business not how to get a disruptive or innovative idea into a market at little to no capital. and PhDs tend to be too wedded to their original idea to make the adjustments that an entrepreneur needs to make.
So having coaches is a good idea.. that's why founders set aside 5%-10% to hand out to "Strategic Advisors". whom you give between 1/2% to 5% depending on their level of involvement and strategic benefit.
this means they bear the risk off the advice they give you. something that a large consulting agency won't.
Note that having someone review an existing business plan for completeness or "holes" in your ideas is something you can get at an incubator or even less expensively by attending "meetups" of other entrepreneurs. meetup.com has lots of entrepreneur based events in almost every city around the globe.
and there is no one more able to poke a hole in your business plan than a fellow entrepreneur that is slightly jealous of your idea.