That is a REALLY good way to do it Ned, love it
Especially because when you hold the CL the bar is not "caught" or stuck in anything on the ground - like it could easier with a tethered launch/landing.
Holding another kite is in fact not that good nor safe - we do it often yes, but it is by far one of the worst ways of launching (and landing) IMO, if one were to nit-pick between the three methods.
There are so many things that can go wrong - that I wont even write them all - it would be a long post then
All these risks are eliminated when holding the CL instead
The only situation where it would be more beneficial holding the kite, is when the ground is not suited for a kite at all, and/or if leeward of obstackles so the kite will not sit steady (or both) - then a handheld kite is the only way to launch/land (but of course risky too)
But in "normal" conditions, your idea is so much better and in every aspect much safer for both kiters in fact
A bit overkill maybe, for most kitesurfers yes, but still way more safe than holding the kite