Thomas,
Yes - That technique has already been developed. It works well because the architect can set the bottom line shape of the bunker with artificial matting (not to be wrongly "reshaped" on first rebuild) and there will also be less undercutting creating erosion at the bottom. The top layers can then be left natural sod... However, I'm not such a fan of the thin artificial sod, preferring the natural look with thicker slabs all the way up... So I'm undecided there.
To your other point, some courses spray off, others burn off - same effect.
Sean - I don't think the Troon bunkers look messy. They are very clean, just with grass faces grown on them. I'm not sure that grass faces on sod walls extend the life that much. I'm led to believe that amount of play and orientation have a much bigger effect on how often a bunker needs rebuilt rather than open sod vs grassed sod.
Ally