While the rules are not necessarily arbitrary, they are based 100% on what is profitable in the long term for the service provider
over hundreds of thousands of installs. It's not really about safety, or property protection, or anything else than the bottom line. The company believes they can limit liability (lawsuits and damage claims) by avoiding installs on certain types of siding, or believes that their installers are incompetent to find exterior studs on side mounts (thus jeopardizing the long term viability of the install). Any other rational behind these rules is just window dressing to make the technician and customer feel better about the fact that they do not have control over where the dish will be located. Corporate does.
So keep corporate (Dish Network or DirecTV) out of it as much as possible if you want something atypical. Order from a "local retailer" (though they may sell nationally or out of their market) and get a "local installer" (one who's paycheck
IS NOT tied to corporate quality control checks).
Go to
www.FTAInstall.com. Look on the list for someone who installs DirecTV, give them a call, and ask if they can order through them. If they can't, they should know someone who can. Or you could try to change the nearly inconsequential policies of multi-billion dollar company over the next several years.