If he can offer the choice of maybe an F7 and F2, then have an F4.5 as a special order, I can't see anything wrong with that.
Do you really think customers will come in, and say "I want an Icon F4.5"? I really believe the majority will look in store, and maybe ask for an Icon if a friend recommended it. People ask for bats by name. They have a "Kahuna", they have an "Icon" or a "Scoop" some may even have a "Mongoose". They then buy the grade which they feel most represents the standard of cricket they play, or what they can afford.
Now when a customer comes in, and asks for an Icon the retailer will reply "Yes, sure - F2, F4.5 or F7?"
99% of customers will reply, "What?" and this is why I think the whole F2, F4.5, F7 is superfluous. And just adds confusion.
Edit: Let me add though - historically that is how I have felt that bats have been bought. There is no reason to say why with education and support from retailers, and education of the customers that the different face types can't become an option without being too confusing.
I'm not a fan of giving customers too much choice on core products, but GM are giving it a go and I guess we'll see how it fares.