BBK/CV
Interesting...
Certainly we're cleared to use the Boeing approved and published "Alternate MCP Setting Technique using VNAV"...which as you say means checking the VNAV profile carefully and if it's OK then setting the highest of any closely spaced SID constraints on the MCP.
It's supposed to reduce crew workload but if that increases the R/T Loading because ATC see something they don't like I guess it'll be back to basics...
I'm just thinking that if the initial level is set then that's more of a "fail-safe" rather than "fail-dangerous" option perhaps?
Might not be - some SIDS (can't think of one at LHR/LGW, but they do exist) can have particularly cunning combinations of step climbs on the SID which will catch you out if you get distracted (e.g. by an R/T call
and forget to wind the MCP up at the critical moment.