but a Forward Hydroplaned FSmash is extremely difficult.
It is, and I have yet to do it on purpose or see anyone do it on purpose. Pivoting works just as well. Plus learning to pivot has more applications and options. There is a way to do a FHFS across entire stages, like FD, without having to master that pesky angle. But in order to do it, up basically need an extra finger by your thumb to you need to give up an entire button on your controller.
While holding down an attack input, shellshift. A few frames after Squirtle is fully turned around, flick the C-Stick in the upper 45 ridge in the opposite direction you are going to travel. Timed perfectly, Squirtle will pivot and you will soar out of your shellshift (2/3ish of FD). If someone could explain why you can get so much more distance with the C-Stick pivot as opposed to the normal analog pivot, I would be interested in hearing it.
I wouldn't consider this method useless. I set my L button to an attack input to do these tricks. It's Squirtle largest hydroplane (if not tied with an actual FHFS) and it's commitment-less, since he is in neutral and can simply take one step to stop all momentum. I've gotten quite a few KOs out of this blank hydroplane, since my opponent doesn't expect the sudden, large distance. There are also some other tricks you can do, but most of them are almost useless for anything but style.
I will give the maddest of props to anyone who can master the FHFS using the impossible angle.