The typical Apple Store is about 8400 square feet, vs about 2400 for Radio Shack. Given the number of visitors Apple attracts (to play with their toys, all of which are set up and working, unlike RSH or BBY), a converted Radio Shack location would be impossibly cramped.
Despite its stores' larger area, Apple achieves around $4.6k annual sales per square foot, the highest of any retail store. The corresponding number for Radio Shack is about $400.
If others did the same, businesses like Rotten Robbie's and Arco Stations would be way up there. They don't "pump" up their store figures the way Murphy seems to be doing with yard sales.
I love PCs and build them/program/use them the most now, but I also have continuously had Apple products since I commandeered my then still-future mother-in-law's Apple II in 1977; and since my first Mac in 1984 when I borrowed money to get it. I am not a "fanboi" but have watched and studied and even programmed Apple products for years. (I have other Apple connections too.)
After you get used to working well on Windows, the Mac interface and dumbed-down functionality (and worsening, just like Windows too is being more toasterized!) (including on "i" products) just drive you BATS! You can customize Mac a lot to compensate for the default Apple interface problems, but that's one more thing to maintain, and when you are doing that on multiple computers it becomes impractical. And iOS (iPhone, iPad) is great for the grandbabies but its dumbed-down-ness is baked in.
Anyway, despite the above I overall LIKE both Apple products, and Windows powered products (even fully updated Vista 64 which is actually a great OS). And I want an Apple Store closer than 100 miles!
SO, more to the point...
I do not think that enough Radio Shack locations are very good any more, so I do not think the idea of using their stores is great. (Personal observation as a real devotee to Radio Shack since the 1960's, though they too dumbed themselves down into oblivion.)
However, the initial point you were responding to was by SamAdams76, that Apple does not have enough stores. Especially in smaller cities. I agree with SamAdams76, and wish they had more stores.
But Apple gets more stores, I do not think they all need to be as big as their present average size which you cite.
I live fairly centrally within a 400,000 population center of about 4+ cities and many burbs, and towns, but I have to drive about 100 miles north or south to get to the nearest Apple Store.
We have a little Apple table in our relatively little Best Buy (and I think the Samsung people mess with it from time to time). We have the usual few Apple things at places like Target. And we have some Apple stuff in the bookstore of our major and well known university if you are in the mood to venture there and get your car ticketed. That's it.
You can't even buy "AppleCare" on a new iPhone (if you delay much after buying it) without taking it 100 miles to be inspected in person at an Apple Store!
A lot can still be done over the phone in handling issues, but Apple misses out on really endearing themselves to their customers by only being in the really big cities.
No surprise, then, that Apple leans toward "blue," a company whose products seem disproportionately favored by liberals (and others with fascist tendencies): their stores are mainly in the "blue" zones where liberals live!
But Apple does need more stores in my opinion, and those stores in the smaller cities could be SMALLER in size than the giant size you quote, if there were more of them.
The main problem, of course, is not just location and space, but the cost of maintaining trained people to work when they are so spread out. They might have to hire more orthodox Americans, too! Maybe that's the problem?
No doubt hyper-successful Apple has already considered everything being suggested here, and have their own studied reasons for not doing just what I want! Dang it!