Call me crazy but wouldn't the lowest possible TA be more sensible? Platform altitude a-la Paris/Amsterdam/Frankfurt/etc with all SIDs climbing to FLs. Would mean no QNH change on departure (1013 before leaving the ground) and only one at the very end with very little chance of it changing before landing. All this talk about continuous climbs is complete nonsense, that depends entirely on airspace design and atco brain power.
Terrain avoidance is much less of an issue now than it was in the past, standby altimeters set to QNH permanently combined with ATC seem to look after it well enough.
Posts this in the wrong forum originally, apologies if it looks familiar.