Only thing I can add to the werx is on the internal Laney thing....
Keep it ~out~ of the Hammond. It will be heavier, hotter, and harder to work on should the need arise. It might even cause some noise issues due to having that much more RF producing stuff all wedged into the Hammond's lower house. And if you need to place the amp elsewhere due to projection issues (or lack thereof) the ~loose~ amp certainly makes that a breeze!
I went through that same hole thing .... in 1977. (see attached funky pics of my M100 rig .. The Barbarian .. from 1977. "Fire Hazard" would have been a more appropriate name I think!)
As to the rotary sim .... BOSS RT-20 .. all the way. I don't know how it compares to the Neo, but I had one of the Boss units. Used it with an XK-2 and my M3 ... wonderous. Headphone out as well. Very cost effective.
But just to get it said ... you can get a "junker" Leslie and DIY the heck out it for your purposes for (probably) no more money than the Boss thingy. Find a Leslie with no amp or a dead amp and use the Laney to drive it (see my sig). The Laney can still be used in parallel for adding key click and reverb. "Rotary reverb" doesn't sound so good, so you may wish to keep your reverb tones from the spinning whirlygigger. The paralleled Laney would provide a fine service in that role.
You'll discover that there are about "a hundred right ways" to do most anything with these old organs.