Back off, fellas. I've got this.
You say he has decent groundstrokes but dislikes net?
I play with and against a player like that. Just lost to her this week, so it is all fresh in my mind.
She is a singles player and may well get bumped up to 4.5 on the strength of her groundstrokes. She does not volley if there is any other option.
She plays one of two ways. When her partner is serving or receiving, she will start at net and then backpedal to the baseline immediately. I do not understand the logic of having her start there if she is going to backpedal, but perhaps some partners insist that she start at net?
Or she just plays the entire point from the baseline, which I actually think is more effective.
So. Just tell this guy to play two back with you. Either he will do well with his groundstrokes, or he will fail from back there.
Now, it is challenging to partner with someone who plays that way. Should you come in when you are serving/receiving, and if so, how? Well, you have to figure it out. If his groundstrokes are good enough, he can perhaps get you something weak that you can approach on.
When I played with the lady I described, I waited until she got a ball. As she was lining up her groundstroke, I would sprint to the net anticipating that she was going to set me up, and she usually did.