Back to Back Lavatories

I am remodeling a bath that has a lav that is back to back with another lav in an adjacent bath (i.e., both baths share the same wall for all plumbing). Attached is picture of fitting that is now serving both sink drains: plumbing supply fellow called it a double ell.

Distance to main drain/vent stack is about 30" (see second photo). I'd like to move this fitting slightly closer to the main drain/vent stack, and I thought I would replace the existing fitting with a PVC fitting. The closest I have been able to find is a fitting that has an additional hub, presumably for a vent (see third photo)? Can this fitting be used for this application (assuming I cap off the third hub)? If not, is there a pvc fitting equivalent to the fitting that is now in the wall? Finally, the lav on the opposite side of the wall is a double lav, where the third lav has no trap of its own, but feeds (via thin walled pipe) to the trap of lav that is connected to the fitting in question, on the opposite side of the wall. I assume I could leave this configuration, but since I have the wall open, is there a better way to go about the design of the double lav? As you may be able to see from the picture, space is very tight, its a 2x4 wall, and I want to avoid having to do any work that will require making any connections to that drain/vent stack. Thanks

fitting

There are PVC double ells, but why wouldn't you just remove the brass one and relocate it at the point where you need it. One thing you might check first, however is whether the bottom of that copper tubing is ready to fail.

I would like to have trap adapters coming out of either hub of the double ell. Right now, I have a short length of cu pipe sweated into the ell hub, and then the chrome trap arm sweated into the cu pipe. I can't imagine successfully getting all that un-sweated, cleaned up, and the successfully sweating trap adapters to the existing fitting, particularly since part of the fitting is now buried in the adjacent wall. I decided to go the (easier) pvc route, and since the pictured PVC fitting was the closest I could find, I was wondering if it would get the job done (assuming its ok to cap off the extra hub). I was planning on reconnecting all of this to the existing drain line via a Fernco coupling. I assume that there are no vent issues here, since I am very close to the main drain/vent stack (wet vent?).