If you want to try something different and save some dough, try all pork burgers. Brat burgers are a big thing here and loose brat is sold all over. Honestly, they would likely win over GB if you have a good mix and grill them. Another one is "pizza burgers". Have not run them in a long time (that needs to change) but also big here. Use an italian sausage mix, sear/grill, top with mozz, and pizza sauce. Swear I posted it maybe it's in another thread but ground pork + GB (like 50/50) for sloppy joes works insanely well. Same for meatballs and loose meat spagetti/bolognese. Back to your original question, I think you unfortunately need to get the pork in background at like 20% range for it to remain "hidden" and keeping it mostly beefy tasting.
Here's my brat burger writeup.
https://www.smokingmeatforums.com/t...h-coarse-grain-mustard-on-pretzel-bun.311151/