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It's still only made of plastic though, not much better... You could DIY something much more secure with a pair of these (or even your original suggestion), a ground anchor mounted to the wall and either a tarp/tarp+polycarbonate roof to keep the weather off. If you're happy mounting it directly to the wall then let a proper security product do the job for you rather than trying to combine them.
That security of that mount doesn't look good, that wire could easily be cut.
What about a Cycloc Solo for each bike?
http://cycloc.com/cycloc-features-Solo.html
That allows you to use a D-lock to lock the bike up, much more secure, and then a bog standard cycle cover or tarp over it and held in place with a bungee.