Could you use a radio control servo and a servo tester to work the valves. I have seen this solution work for Columbia's regulator.

Brian

I could lend you a hacksaw to shorten your tender…

I've seen quite a few contrivances to operate loco valves from the rear of the tender. It usually involves a number of controls attached to a cross-plate secured to the tender. The controls are usually rotary (for steam valves) and generally involve a long operating rod provided with a couple of universal joints. The "loco end" of the long operating rods also need some kind of bearing/support.

There needs to be some provision for changing the effective length of the rods as the tender and loco negotiate curves. This could be a pin through one part of the rod and a slotted tubular section on the other. Water valves can be sited at the rear of the tender so that their operating valves can be sited where it suits you.

It depends on how you feel about your loco; if you want it to look realistic when you aren't using it, then it would be an idea to have all the jiggery-pokery removable – but that will add to the complexity of the design.

It does need very careful thought to make the regulator control safe; you don't want to be faced with the loco running away and you being unable to shut the regulator. Hence give a bit of thought to fail-safe design of the linkages so that if the loco-tender coupling parts, then the loco will coast to a halt.

You've got a big task to operate a pole reverser remotely, but a screw reverser might be susceptible of remote control.

My advice is to stay away from electronic/radio operating devices and use something mechanical.

Re the effects of curves on control-rod lengths.

I propose it might actually be negligible, and certainly easy to accommodate.

Even at this loco's curve limit, the linear movement will be small enough to allow the rod to slide through a bush; but you could make a short telescopic section based on either a slotted tube and cross-pin, or small-section square tube and bar.

I'd think the injector steam valves the easier, not harder, to arrange, assuming they are on the turret and have spoked-pattern hand-wheels.

Lever-type reversers: I have seen an extension control used on a miniature traction-engine, I think based on a tube ending in a clevis gripping the handle, and an internal rod that operated the trigger, with a suitable grip and push-button on the operating end. A Bowden cable might work but would need a return spring on the lever.