I'm not sure if a palm bonsai is possible. When I say that, I am not trying to stop someone from trying, but I have never seen one and I assume there is a reason

To start with, palms only have one bud, and if you trim or damage the bud you will kill the whole tree. Next, if you trim the palm fronds, you actually accelerate growth instead of restrain it. I think people can plant palms in small pots and "call" them bonsai, but I'm not sure they would meet the classic definition. Certainly I have never seen a "true" palm bonsai like a coconut, king, queen, date, or fan palm.
By the way Sago Palms are actually not palms at all. Rather, they are Cycads - a very primitive tree that is more closely related to a tree fern than a true palm. You can stunt their growth by restraining roots - so if you want a smallish Sago in a pot it doesn't sound that difficult to maintain. I agree however it look kinda like a spiky fern (I have about 8 sago palms of various sizes in my landscaping and like the way they look).