BrahMos should work very well. There are air launched versions of the missile. High altitude wouldn't be a problem.
What I'm more interested is in knowing it's targeting and detection capabilities for Air launched version. How exactly is it It used? I'm pretty sure the sukhoi can't use its Air to Air optimized radar to tag ground targets. So that means either the targets are predetermined and stored in the missile or a ground based radar does the job.
Sure, the Brahmos can operate at high altitude. But launching from a plane and launching from a ground launcher is another matter. The Indian media claims that they have moved ground-launched Brahmos missiles to Ladakh. Theoretically, they should work with no problems.
But launching is the easy part. How would the missile actually perform for the rest of its flight is the real question. How would it perform on mountainous terrains of the Himalayas? The navigation system on the Brahmos is optimized for naval combat, ie: flying over a featureless sea while scanning for targets. But how well then would the Brahmos fly around the Himalayan mountains to hit Chinese targets on the other side?
I'm assuming that Brahmos won't fly like a true cruise missile because of its 2.8 Mach cruising speed, coupled with its relative lack of maneuverability vs dedicated cruise missiles. Which means, the missile will have to fly to its target via a lofted trajectory. Essentially making it easier to detect and intercept. This is inferior to ballistic missiles because ballistic missiles travel far faster to the target (around Mach 7-12). Most of the modern Chinese SAMs have a top speed that can match or exceed the speed of the Brahmos missile.
If I am wrong, and the Brahmos is more versatile than I think it is, then India should have conducted a test of the missile at Ladakh or AP. India is not a secretive state like China. Any success, no matter how small or deluded, would surely be on their news.