The operation of the disposable camera is for the most part simple, maybe, but it's not exactly ideal. There's still the matter of loading and unloading the film. Since disposable cameras aren't intended to be loaded by consumers, it's nowhere near as easy as with the sort of rear panel you find on ordinary 35mm cameras. At least with my camera, loading the camera requires rolling the film around the pin across from the canister, pulling it out of the canister as far as it will go. Since there isn't any external mechanism for turning the pin, it is necessary to do this by hand, rather tediously, in pitch darkness. Then the camera must be reassembled, snapping the back to the front, also in pitch darkness. This must be done without disturbing the sprocket mechanism that counts off frames, or it will disengage completely, in which case it must be re-engaged by hand, once again without being able to see anything.
The point here is that while the basic operation of the camera is straightforward, if you decide to modify your own disposable camera in this way, you should be sure to learn the details of its mechanism well enough that you can disasseble and reassemble it blindfolded. Practice with an exposed roll of film, so you can check what's going on, and make sure you learn what can go wrong before it happens just as you're getting ready for a photo shoot.
Alternatively, you could buy a non-disposable camera which is meant to be loaded by the consumer. Most places, these will cost significantly more than a disposable camera. Fortunately, a "good" camera isn't remotely necessary, so exceptional deals may be had at thrift stores. I just bought three assorted cameras to experiment with, totaling less than I paid for the disposable camera.
Besides making it much easier to load the film, non-disposable cameras offer some other benefits as well. They are generally more durable. Their mechanisms work more smoothly and reliably. Many of them have threaded holes for mounting securely on a tripod. Some have slidable lens covers that can be easily adapted for use as a manual shutter. The chief penalty that you'll pay is that they're generally heavier, and often bulkier, than a disposable camera.