If I invest in a company I'm looking for management skills from the management, not technical skills or detailed knowledge that their underlings should have.  The majority of management skills transfer between ANY two areas of business if the companies are of a smilar size (some skills are needed more in small companies, others more in large ones).

MP is effectively the CEO/MD of MG.  The only skill-set that matters much is whether he has the skills needed to be the person in charge.  EVERYTHING else can be hired.  The decision of whether to invest or not rests solely on whether you:

a) Believe he CAN fill that role well (i.e. is capable).
b) Believe he WILL fill that role well (i.e. will deal fairly and honestly with investors and put in the effort needed).

Whilst it WOULD be a bonus if he already had experience running this type of business that's all it would be - a bonus.  If he's capable of filling the first leadership role then one of his first hires (or consults) will be someone with the industry-specific knowledge.

A large proportion of business failures are ones where the leader has MASSIVE knowledge of (and experience in) the industry/sector.  They fail because their experience and ability isn't in the role of leading a company.  Open two threads promoting 'businesses' on these forums and you'll almost certainly find at least one such - quite probably two (you may have to check back in a few months to be sure about the failure bit).

I'm not making any comment on MP's ability in this post - purely othat you're not even looking at the right thing to measure, so arguing over the measurement itself would be a total waste of time.