I know this is old but one of the only two threads that exist on this topic. the other is here:
https://www.eevblog.com/forum/beginners/help-desoldering-through-hole-components-with-an-aoyue-968a/msg487784/#msg487784Thought I would keep from clogging google with another thread and just piggyback here.
I found this post and the other because I have the 968A+ and I have made a simple modification to attach a desoldering gun to it. The short answer is that with a jumper wire between pin 6 and the back of the "smoke absorber" vacuum switch (or 2 other places depending on how tidy you want it) you can make this work as though it was always meant to do it! You'll also need to make sure of the wiring of the desoldering gun and may need to replace the connector it comes with like I did.
I recently began a significant salvage effort on a pile of old electronics. The solder sucker was just not cutting it not to mention my hands were starting to hurt and I hadn't even finished one board. I don't need/want yet another box on my bench and I had the same thought as you - this thing has a very strong vacuum in it already, can't I just use a desoldering gun for it?
The Aoyue desoldering gun has been discontinued, so I looked for other options on the Amazon etc. I landed on the one below but it is 8pin so I also ordered a few GX-16 6 pin connectors to fit the 968A+. I had checked the specs of the station it is compatible with and it is 75W so I figured it was safe for the 70W of the Aoyue. I cracked it open to figure out what wires did what, drew a simple pinout, then wired up the new connector.
https://www.amazon.com/gp/product/B07Z76P231/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1Simple trace tracking showed me what connects to the switch, which pulls low to tell to controller to turn on the pump. Therefore, the switch can share ground with the thermocouple. Thus the jumper from pin 6 to the vacuum switch and the switch at the gun handle connects pin 6 to controller gnd.
Plug it in and voila, works beautiful. Happy to put up pics or help anyone interested in doing this.