Unless you desperately need to read more than 10 books simultaneously, I don't see why you feel the need to circumvent the restrictions.
Note: I get funny looks all the time for being in the middle of several books at once, switching between them

but I've never gotten into the middle of over 10 at once

kind of overdoing it if you ask me.
You can only borrow 10 books through KU at a time (but you can switch those out as often as you want).
However, you can certainly buy as many as you wish, and keep them all on your Kindle -- limited only by the physical storage capacity of the device (~3500 average-sized books).
KU books work like library (OverDrive) books, which is to say that Amazon will message your Kindle to delete the book with that ASIN once you've returned it.
You don't get a choice.
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Regardless, MobileRead does not condone theft of library/KU ebooks, however it is justified.
Doing so can be grounds for a permanent ban -- I'd avoid going near such lines of inquiry.
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