I think that it is common in commercial brewing to find limited amount of specialty malts in a beer because of the sheer difficulty of keeping so many malts in inventory, but aside from that there is no limiting factor.
Off the top of my head here are the malts I have in stock right now, and I bet it rivals most of the homebrewers on this forum.
Best Pils
Best Vienna
Best Munich I
Best Munich II
Best Wheat
Best Smoked Malt
Briess Pale Ale Malt
Briess Midnight Wheat
Weyermann Cara Red
Weyermann Carafa Special II
Thomas fawcett Rye Malt
Thomas Fawcett maris Otter
Thomas Fawcett Roast Barley
Thomas Fawcett Dark Crystal
Franco Belges CaraVienne
FrancoBelges CaraMunich
FrancoBelges Chocolate Malt
Flaked Rye
Flaked Barley
(there is probably another 10 varities I am omitting accidentally)
Now, granted, some of those are just a couple sacks a piece for small 1 bbl batches but I can plan any recipe I want and order those malts at any time. But for convenience factor I do try to minimize the amounts of malts that go into my beer. especially the flagships. For instance I order Best Pils, Munich, Vienna and Wheat my the pallet (each) while the specialty malts I order as a mixed pallet with maybe only 2-5 sacks on each order.