So this project has been bumped back up the list, after a slight mishap with my Cyclone (all I'll say is running a 25mm boring bar into the chuck wasn't a good move), and as I'm still waiting to find out if the parts needed to fix the Cyclone are available, this project is getting a lot of attention, as even if the Cyclone is fixed, I'd like the extra capability.

The current status is an A2-4 6000rpm spindle has been ordered, and is now crudely modelled in Fusion for the purpose of figuring out layout/dimensions.

I'm currently fleshing out a couple options.
My main use for this lathe is for gang tooling, with live tools, however I have discovered turrets are available for less money than I thought.

For those unfamiliar with lathes, the big benefit of gang tooling (row of tools mounted directly to the cross slide) is speed of changing tool. The limitation is part size, and the number of tools you can mount.
The benefit of a turret, is you can machine relatively far larger parts, but the tool changes take longer.

In terms of machine design, gang tooling doesn't need much bed clearance as long as tools are on the spindle centre height, whereas a turret requires far larger clearance. To give an example, the 8 position changers I've looked at, typically require 200mm clearance below the spindle centre height.

I'm currently weighing up whether I want to go to the hassle of designing that high a headstock, for something I might never use.
If I knew I would still have the cyclone, I probably wouldn't as the cyclone can handle up to ~120mm diameter parts with a fully loaded turret, whereas if I only have gang tooling capability, I'd be limited to either only a few tools with limited Z travel, or small diameter parts.

I'm now off to model a turret in Fusion