There is a wonderful essay that addresses this topic specifically in the 1993 version of "Hazards" (by Aleck Bauer, originally published in 1913). The essay is titled, "To Rake or not to rake bunkers? It is written by Philip A. Truett, who was the Captain of Walton Heath Golf Club at the time. I thought I might retype the whole essay, but it is a bit too long. Suffice to say, for those of us who believe bunkers are lacking in their ability to create true risk/reward scenarios in today's game, Mr. Truett made many solid points.
I think that Tom Doak is onto something when he mentions the internal contouring and the different sand characteristics from hole to hole or bunker to bunker. Taking the predictability out of every bunker shot would start to create that creeping doubt in the players mind as to whether it is worth the risk of challenging it. I also like Biarritz's comment of a deeper bunker. (In fact, I have a preliminary design for a par five that would include a deep pit fronting the green. I was thinking "only" 10-15 feet so I might need to reconsider. Two fairway options around either side would create some real value for the players that want to go for it. Almost exactly as you described.)
Beyond that though, I think the problem with the bunkers is that there are too many on most courses. Flanking every landing area and every green with bunkers on both sides pretty much forces the architect to tone down the hazardous nature, otherwise the golf course becomes a playability nightmare. I think that there has been a trend to create more visually appealing courses at the expense of solid strategic courses. More bunkering might lead to magazine covers, but it hurts the overall balance of strategy and playability.
If a golf course's merit is in its ability to challenge the finest players while still being playable to the average player, then less bunkering but more penal bunkering might be the answer. I would take Tom Doak's suggestions regarding sand variety and internal contouring and throw in Biarritz's comment about deeper bunkers as well. If you take this step though, then you have to be sparing with your use of the bunker. Each one should have a solid strategic purpose, and the golfer who doesn't want to risk challenging it should have an optional line of play and plenty of room to play away from or around it.
I rarely bunker both sides of a landing area or a green. There is usually that option of playing away from the hazard, though at the risk of giving up a good angle to a pin, or dealing with a contour that funnels a ball the wrong way, a longer more difficult putt, etc. The small things that cost you a partial stroke here and there.
This subtle stuff that makes the game fun and challenging doesn't necessarily show up on TV, a magazine cover or in the glossy brochure though, and as a result it can be a real challenge convincing your client of the merits.
In order for the architect to properly incorporate these "hazardous" bunkers, they will need something that most clients don't want to give up...width. You need width to create the options and the risk/reward strategies and the room that will balance out the difficulty presented by these stronger bunkers. It is like pulling teeth to try and get some width and some room from the developers. As a result, things get modified and softened.