Are you willing to go to trial court then pay for the appeals court and then still be stuck? You are the one that signed on to the HOA or bought with it in place. This is first semester law school. Read it!!!!!!!!!!! again and again. What is concidered "unreasonable to the point of violating your consitutional rights" is compared to what you already signed off on as reasonable.
Sell your house quickly, or get some FRANK ($) legal advise.
As far as "aesthetically pleasing" you'll probably need an architecht and a VERY local historian/politico to not only agree with you but prove the HOA definition to be disjointed or diconnected to the area, town's history, or OBJECTIVE of the HOA.
Anyway, in my decades of experience it is impossible to "cat proof" a yard as it is impossible to "squirrel proof" a yard.
Follow mother nature, and you neighbor, get an outside dog that likes to chase things.