Olivier,

The best for me, is to have the possibility to recompile the MPLS kernel module with the new value the MAX_LABEL_STACK and then let our Segment Routing implementation read this value to determine what's feasible.

Yes but we still need a default value.
You have also to see the perf impact, now the current mpls entry size in linux kernel is under
a cache line, even using 12 stacked labels, we are always under a cache line but beyond
this value we're going to see performance issue.