I have had a noseless saddle on my bike for ages and just for the fun of it I mounted it on a unicycle. The saddle is an ERGO The SEAT® by Lycra Gel Saddle
I first tried it with only a handlebar and it was very comfortable on the butt however it required quite a bit of force pushing back on the handlebar to stay on the seat. Overall on a 2 mile road test it was not that comfortable to ride because of the strength required to stay in position.
Next I added a "Groin Support Bar" to hold me back on the saddle. I rode about a mile with no padding on the groin support and is worked quite well. I then added some padding on the groin support and adjusted some so it fits correctly. On an 8 mile road test it preformed very well with no adverse effects and no need to "rest" my butt as needed on my normal unicycle saddle. (Actually my normal saddle on my 36er is quite comfortable but just have to take a minute or two break or peddle standing up for awhile ever few miles on longer rides.)
It is a little cumbersome to free mount the noseless saddle because I have to get the uni vertical, swing over the wide seat and work vertically down between the saddle and groin support. It is quite secure once in and dismounts off the front or back don't seem to be a problem.
Since I mostly do 36er road riding I'll get the height adjusted on the 36" and give that a try.

Update #1.
I installed the noseless saddle/handlebar on my 36” Coker. I’ve put about 20 miles on it with 14 miles in one setting. In general it seems to be about three times less annoying then a normal uni saddle. I can go about three times longer before I want to take a short break. On a normal saddle I normally go about 3 or 4 miles before taking a short break, mostly to give the butt a break but it also gives the legs a break. On the noseless saddle I can go much longer distances before the sit bones start to annoy me. The down side of that is that my legs do not get a rest every so often and at the end of a comparable distance my legs would be more fatigued with the noseless saddle. The other thing that affects the legs is the seat height. Because of the necessary lower saddle setting my legs get more of as workout on the noseless saddle.
One disadvantage of using bike saddles on unicycles is that there are no bumpers on bike saddles. A few drops could do quite a bit of damage to a bike saddle. I added a tuff HDPE rear bumper on the noseless saddle and that also serves as a “kick stand”. I also added a front bumper on the handle bar so it will take a beating with out any damage.
I did add a loop hand grip on the handle bar but it is too close to my body. I need to add a longer hand grip and see it that works better for road riding.

Update #2.
I put the ERGO The SEAT® saddle back on my bike and made a homemade noseless saddle. The homemade one is a little larger and contoured to fit my sit bones and butt better. The basic idea was to shape the saddle base (rigid foam in this case)to a comfortable shape without any padding. Then add a little foam, 1/2" in this case. It is more comfortable then the store bought noseless saddle and is by far the most comfortable unicycle saddle I have ever ridden. There are disadvantages with this set up but just based on saddle comfort alone, it would be hard to beat.

Update #3
After putting more then 100 country road miles on a noseless saddle I have a better idea of what works well.
I made an air supported noseless saddle. After looking at many factory made seat cushions for motorcycles and general use I noted that air cushions were quite popular and highly rated. Many unicyclists know that air saddles were tied and sold in the past. Even though some reported that they were fine, it seems that most riders did not like them. I believe there are two reasons they are not popular today. 1. Many reported problems with the inner tube sifting and not staying in place. This could likely be fixed but there was a bigger problem 2. I believe the very idea of a normally shaped air unicycle saddle is/was flawed. With an air saddle equal pressure is put on all areas in contact with the saddle. That is there is equal pressure on the sit bones, butt cheeks and more sensitive perineum area. With the general idea of removing pressure from the sensitive areas and adding more pressure on the less sensitive areas, the idea of an air unicycle saddle just does not work. I see one report on this forum, “I made one a while back, actually turned out perfect, looked good, the tube stayed where it was supposed to stay while riding. However... they suck. after not longer then 5 minutes my entire crotch area was numb due to pressure being applied to just...everywhere. The first 5 minutes are fine, the saddle is actually more comfy than any other saddle at the beginning of the ride.” I also saw that Ed Pratt tried an air saddle and reported initially that is was good. However after some time, he was back in pain again, as he was essentially on his whole round the world trip.

However with a noseless air saddle there is absolutely no pressure on the sensitive perineum area and the idea of an air saddle makes a lot of sense. A noseless airless saddle uniformly distributes the pressure on the sit bones/butt cheeks and maintains the uniform pressure under the legs as they move up and down. The air saddle I made is 10” wide and about 6” long. Just considering the pressure due to the contact area, it is clear that there much less pressure on this saddle. And the pressure that is there is where it belongs.

To date I’ve rode the air saddle as long as 2 ˝ hrs on a single ride with no break. After that time the noseless air saddle felt as comfortable as the instant I started. I had absolutely no adverse effects from the saddle. Based on saddle comfort I could have rode much further and even then I’d be limited by leg fatigue or being late for dinner.

So to date I'd rate the comfort of saddles in this experiment as:

1. My favorite road riding unicycle saddle (UDC Club Saddle), good for a 100 mile day with no padded shorts - Fully serviceable with a break now and then.
2. Off-the-shelf noseless saddle without handlebar – Not rideable.
3. Off-the-shelf noseless saddle with handlebar and no groin support – comfortable but not recommended due to the force requited staying on the saddle.
4. Off-the-shelf noseless saddle with groin support – About three times more comfortable then #1.
5. Homemade rigid foam noseless saddle – About five times more comfortable then #1.
6. Homemade air noseless saddle – Much greater then 10 times more comfortable then #1.

For now I’ll leave the air noseless saddle on the Coker and my normal saddle on my 36" Nimbus. Maybe I can come up with some alterative to the groin support thingy.