It's hard to know what flavor profile you're reaching for. If you're looking for "Southern" or "Comp," you need to be sweeter.
Drop the amount of broth -- or better yet, use a concentrate. You can go with a home made glace, or use something like a product like Better than Buillon.
The only sweetener you're using is apple juice. If you want to stick with natural (more or less) juices, add a cup of white grape juice. If you're worried about your butter ratio (which is very, very high already), add an additional stick of butter.
Your seasoning profile appears rather dull to me. It needs some herbal complexity (sage, rosemary, whatever) and a little heat.
For the heat, while it's not all that common in 'q, you might want to think about white pepper. It's more or less colorless, and generally sold pulverized. If white pepper doesn't sound appealing, just use cayenne or hot sauce. You won't use enough to discolor the meat.
My practice is to cook an injection solution long enough to blend all the flavors, then strain so that it passes through the needle easily. The extra time and straining allow the use real of real onions, real garlic, herbs, etc.
In any case, these sorts of things usually require a lot of tasting and experimentation. Don't expect solid gold your first time out.
If you are thinking about competition, the best advice I can give you is not to stray out of the envelope. Judges want quality, and hate originality. On the other hand, if this is for catering, you might want to get a little more original. My impression of Southern Illinois though is that you don't have a lot more leeway than you would in comp. You know your guests better than I do though.
Finally, turkeys are one thing and chicken another. If you're using whole chickens, or pieces including wings and legs, it makes more sense to brine than to inject. Of course, you lose the butter. But, I smoke a reasonable number of turkeys in the course of a year, and, in my experience, they don't need additoinal fat. Brining and proper smoking technique are enough to insure a moist bird.