Very interesting!
I've used the layering technique several times, especially when the toms in their starter pots have become too leggy. They do eventually 'turn upwards', even if they're not looking very happy, and I suppose the receptors in the underground stems do get more 'grub' as a consequence!
I'd go for your idea John, presumably you can grow them like their cousins (spuds), and earth them up as you go along, but it seems quite a lot of work for an extra truss or two...