Title says it all, i'm just wondering if this is possible, or how easy it would be to make if it is. It would be so cool to be able to use them as a method of transportation in the nether, since lava is everywhere. I've made a few attempts at just jumping on them, only to realize you fall right through them.
Well, There is a plugin called MobRider which lets you RIDE the ghast, but I'll warn you now that you can't see anything, even in 3rd person, they're just too big. Changing that would be a client-side issue too so not much you can do really. Riding them is possible though, dont doubt that
