Hello Martin,
Your mention about the interest to activate summits for more skillled mountaineers at high altitude, makes me think that probably, such summits are rare ones and less activated.
In consequence such activations will probably attract avid chasers looking for “new ones” in their unique summits list.
Therefore perhaps you could expect a huge pile up when starting the activation. Bear in mind dealing with a Pile up at 12 wpm in going to be a bit tough, and assuming you want to keep your activation short in time, there could be plenty of chasers whose would be reluctant to work you QRS…
Anyway, I’d support the idea of doing it on CW for ease of auto-spot and the MTR is the best option.
My tip for you in order to make your friends in the summit more cooperative, is that you can involve them in the deployment of the antenna.
Train them in the task of preparing a hole and setting up the antenna wire and they will feel involved in your success. As a bonus you will save some time while you are preparing the rig and log, right?
In the other hand, choose carefully an antenna that can whitstand severe wind up there… a short loaded monoband vertical, as others suggested, is a good chance.
Look forward to work you QRS, Good luck!
73 de Ignacio