I can highly recommend the Hope Pro2 hub. I have the trials version with the 5-speed free-wheel, obviously with spacers and a single cog. Go for the Bolt-in option though. Rather than a solid axle, you have two massive bolts that screw into the hub. You don’t need chain tugs with this system at all, just pull the wheel back and tighten the drive side bolt, then pull the wheel to the middle of the frame and tighten the other bolt. Then add a bit extra to both bolts for good measure. The wheel is dead easy to get in in the first place as you’re not trying to get an axle through both sides at once and you can slide the wheel in from in front of the drop outs if that makes sense.
BMX chains look better, should be more robust, but seem to just stretch more. Not run a normal chain, but suspect they would be better. I adjust my rear wheel every few rides as the chain stretches, but you can just run the drive chain until it’s completely shagged as you don’t have to worry about good shifting obviously.
I can also recommend the On One Whippet frame and the X-Lite rigid forks, though I think neither are available new. Whippet is very light and very stiff, so ideal for what would be a light build anyway and the stiffness helps when you’re cranking away at the bars. The forks are 15mm through axle, so more likely to be cross-compatible with your other bikes. If you go rigid, get some huge tyres and run low pressures (tubeless) to damp the trail buzz. it’s great fun and turns boys into men.
I have a medium Whippet in bright Yelllow going on eBay soon if that is of interest, would need a set of swap-outs from On One though for SS use.