I'd like to hear which schema.org itemtype others would recommend using or have used in the case of completing a retail brand's company homepage microdata. Take for example TOMS's shoes:
Example #1 - Using /Corporation as the high-level itemtype one can include a lot of great /Organization microdata, but nothing about the retail store.
<html itemscope='itemscope' itemtype="http://schema.org/Website>
<head></head>
<body itemscope='itemscope' itemtype="http://schema.org/Corporation>
various microdata here probably including Product microdata
</body>
</html>
NOTE: the only schema.org property specific to /Corporation is tickerSymbol & TOMS doesn't have one.
Example #2 - This code would work if TOMS started their own channel of physical retail stores & each location had it's own homepage. However, for TOMS's.com, although accurate schematically & more descriptive at the face, this is incorrect microdata markup for TOMS.com, because /ShoeStore derives from /LocalBusiness - which must represent a physical place.
<html itemscope='itemscope' itemtype='http://schema.org/Website'>
<head></head>
<body itemscope='itemscope' itemtype='http://schema.org/ShoeStore'>
a whole bunch of jabber here
</body>
</html>
NOTE: Since TOMS is virtual & thus can't be a /Store this means you lose really cool properties like 'currenciesAccepted', 'paymentAccepted' & 'priceRange'.
Is this just a 'sit and wait' situation until more schemas are approved for 'virtual places' or is there a validation-passing way to get the best of both worlds?
Assuming you're looking at this more or less from an SEO point of view, remember that the major search engines are currently making only very limited use of microdata, and the schemas you're talking about (Corporation and Shoe Store) are not, to my knowledge, used for anything (yet). So, to an extent, I think the whole thing is largely hypothetical for now.
However, I think it's important to remember that you could use very different microdata depending on the page function. You're asking about the homepage, for which it could be completely valid to add only enough microdata to describe the name and category of the entity concerned. Detailed product data would appear on product pages, more detailed organisational data on the about or contact page, etc. In other words, use the schema that best allows you to encapsulate the main purpose of the page.
Incidentally, they've recently added GoodRelations vocabulary to Schema.org, so the scope for describing products and other business-related data just grew considerably.