The problem is not the assault rule

[K K Rossokolski]

I agree that leaders should be able to call in / plot artillery barrages. However, I have mixed feelings on the use of HQs as artillery spotters. As Mike notes in his post, HQs are fragile and I am very uneasy about moving such high value units close enough to the front lines to establish LOS on enemy positions!

:soap:
It seems to me that, if we have arty spotting and control capability vested at sub-unit level...in other words in a hole in the ground, under fire, in the rain or snow...it is a betrayal of common sense if that capability is NOT vested in higher echelon HQs, which are normally better manned, equipped and housed.
If an individual player wishes to expose his HQs in order to exercise that capability, that is surely his own decision. Game design should maximise options rather than exclude them.