Cs Approach tend to give departing aircraft assigned 030, so the missed approach tK 015 will keep you clear of departing aircraft, and the earlier it's initiated the more separation you will get.
Oh no.
If the departure was given 030, and the inbound was able to execute a left turn like a Pitts, then this may all be well and good.
However, the inertia of the inbound will take them well south of the 15 threshold in the MA, and if the departure has commenced their left turn well before the DER, then things get ugly. Likewise, the departure may have HDG 360 with TWR visually separating, and they would not be expecting the arrival making an early left turn.
Recently had a B717 go round off the ILS due to conflicting LOC indications. They turned left about 7DME, but advised they were doing so early. In this case, I can understand the reluctance to follow DAPs and the immediate advise allowed us to take other appropriate action.
If a MA is commenced early, then climb, advise ATC, and as soon as you're above RLSALT (or visual, if the problem isn't Wx related) we can initiate a turn as other traffic permits.
travelator - sounds like you've got a pretty good grasp of the issues involved.