Designing a volume & power switch for an old McIntosh Preamp

[neevo]

Hello everyone! I have over the past few years been restoring a beautiful McIntosh C20 Tube Prepamplifier. These date back to the 1950-60's and are a glorious bit of kit. My restoration is now complete and I had to make a few parts along the way as these things are no longer supported by McIntosh for a lot of items (understandably so given the age). I documented the whole build process for anyone who is interested on a popular Audio forum.

My latest project is to build a replacement volume and power switch as these are known to go bad on a few vintage McIntosh machines and are also no longer supported. There are reproduction parts available which I have in my C20 (and its working fine), but they are supposed to be all over the place in terms of quality... so I am looking to make a better version that also has the option of being rebuildable if required and also tunable to dial it in perfectly.

The original C20 volume potentiometer has 4 wafers (audio) and a rotating switch all in the same assembly:



The repeated use of the switch is what seems to kill these pots, plus the balance between all the 4 wafers is not even that good

My design uses 4 stepped attenuators but where I am getting stuck is the switch mechanism and thats where I need some help:





I am keen to get rid of the mechanical switch if possible as I think I can get more control from a low voltage wiper and activate something like a relay or Triac. I could use a microswitch, but I find them a pain to set the trigger point and given the stepped attenuators ativate in 10 degree increments, I really want to activate the switch on the first 1 or 2 steps. So my thoughts were to use a voltage divider network to trigger a triac, all using the 120v line voltage on the original switch:



When I simulated this, it looked like it would work but I am not 100% sure and keen to have some experts help me understand to make sure its effective + SAFE! Ideally I would like to put this all on a PCB on the end of my design which also would need to allow for the 120v and 35w of power the C20 uses. The simulator showed only 740mv and 70 uA on the switch, which in concept seems like it will work. But I cannot be 100% sure I haven't used the simulator wrong or made some basic errors.

Hoping to get some guidance here.