Further to the points made by Darko and Mike, don't even think about using PARAM_RAW there! That would disable the cleaning entirely, potentially creating a security vulnerability. If you really wanted to make this change (but please don't - it wouldn't be integrated into core, so your plugin would only ever be compatible with sites which implemented your hack), a better option would be PARAM_ALPHANUM, which would still perform the usual cleaning but allow numbers in addition to letters.
That said, I was contemplating building some kind of H5P plugin myself - are you building a simple resource module to allow use of H5P content, or are you intending to get fancy with it? I'd be keen to hear more about your intentions and progress, and hope you'll be making your plugin available to the community; if you get your code up on Github and share it here in the forums, there's also a distinctly non-zero chance that other developers will be willing to lend a hand... (I can't make any promises, but I might be able to help out at some stage)