I don’t think that stacked kite trains are suitable for crosswind use in AWE efficiency context, as the lower kite will have to fly slower than the upper kite, as the trajectory is reduced.
However, for a pilot (lifting) kite use, a kite train does not have this drawback.
I thought that stacked Sharp rotors would be easier to install. I just realize that some stacked ram kites have be realized, for a playful crosswind steering:
Perhaps more spacing would be required in order to maximize the traction of each unity, although stacked 10.5 cm diameter 50 cm span Sharp rotors spaced to 0.2 m generate almost no thrust loss. And also single skin kites could be implemented. A single tether will be able to relay the set of kites to two lines.
Probably higher spacing would be necessary in power crosswind use, this video having been discussed previously.
If a high level of stability is realized in spite of wind variations, we can then imagine what would be a super lifting stacked kite system where each unit would be as big as possible, and where the height would be unlimited (no problem of trajectory or transmission). The enormous lift gained would then enable a conventional wind turbine to be lifted or, better still, a lighter Kiwee-type (@Kitewinder) rope-drive driven wind turbine tensioned by the pull of the stacked lifting kite system.
This could be a way to meet the conditions for a marketable AWES: efficient use of high altitude winds, high elevation angle and therefore high power to space ratio.
In these conditions the kites are used to do what they do best: fly and lift; while the on-board wind turbine (with ground generator for optional rope-drive transmission) is also used for what it does best: produce electricity.