Wow....if you can make a fast food pattie that actually has flavour, good on you !!. After the major E-coli fiasco over here, all patties at Rotten Ronnie's (mcdonald's), A&W, Dairy Queen, etc, look and taste like ink erasers: grey and flavourless. They are pretty much cremated, and are no longer worth the money. (imho)
I have no way to tell you what a formula should like, but could you start with a grind offering **some** fat? At home, we use the "medium" ground beef. Here's a table on fat content permitted over here: The federales inspct all the time. We use egg, and oatmeal as a binder.
Could you not use powdered eggs, and little water? They are probably quite reasonable at the wholesale level. Would you need to warn folks about allergies when using egg?
http://www.breadnmolasses.com/atlantichealth/id110.html