There is an added cost to the additional fairway acreage for fertilizer, chemicals, irrigation, and mowing. There is the chance that while fairway running into the bunkers will play as intended, the turf may not look as good as rough height turf. It is also a look that may not go well with a parkland design.
I agree with Ray, the best thing is to strip the sod and start again. There are some courses with mongrel mixes of grass that have enough bent in their rough that they could start lowering the height, overseed, and heave the desired result within a couple of years.