Something else to consider is that if you prove this is viable under the regulatory environment and a profitable way for a brewery to sell beer that other breweries in Portland are going to start doing the same thing and create competition in that space. Can you rent space in a pod under an agreement with the landlord to exclude other breweries/beer carts in the same space?
Yes, that's how most (if not all) cart pods work. I would have the only beer and wine service in my pod. I should mention that Rogue does have a beer cart in a nicely-located pod (I just found out about it in my research).
Will your beer cart offer something that makes your experience unique (e.g. randalls, keg hopping, casks) that larger breweries cannot efficiently provide in that market? Will the novelty of your operation wear off when others do the same thing and diminish sales?
Actually yes. Although the concept was based on the idea that a cart was simply the cheapest way to get beer out, I am a big fan of cask beer and basically none of the breweries in Portland consistently serve English ale on cask. The few that do all serve the cask beer ice cold, which ruins it for me. There is, at present, no brewery in Portland that has a particularly "British" tilt. I would be offering English ales and IPA's and would attempt to have some sort of English-inspired branding. As for dry hopping, dry beaning, and the like, that is reasonably easy to achieve when you're using firkins and pins anyway.
With that in mind, would it make sense to try to buy out your own pod where you could necessarily exclude other beer sales and select the quality of food that surrounds your beer?
A few reasons: 1) there is not much real estate that is "pod-worthy" in inner east side Portland that isn't already a pod. What remains isn't for sale. 2) I don't have half a million dollars to spend. 3) If I had that much money, I would open a larger production brewpub in a brick and mortar location.