One of my tractors has a front mount mower and it is a great thing! I've cut about 90 minutes off my mowing each week. The front wheels on my front mount mower swivel, the rear wheels are fixed, the entire mower is fixed to the front frame and driven by a belt. I think the hardest part of rigging one of these things up would be making sure the deck can vertically float up and down with the bumps.
By the way, I tend to agree about the issue of hitting rocks and how the mid-mount mowers tend to hit a lot more than my front mount. I think the tractor tires may displace the rocks and cause the mid-mount mower to hit them? What I am sure of is that the front deck makes it much easier to see, much easier to mow under trees, much easier to mow along landscaping, and it does not hit as many rocks or scalp the ground or cut uneven on rough ground as compared to a mid-mount mower on a lawn tractor.