Well, I've just been through the illegal procedure penalties and there's nothing in there about taking oneself out of play. Nothing. Nada. Nothing in 8.3 about having to be upright to score. Nothing really in the out of play penalties section either, the only thing I can find is about blocking while out of play, but I think that refers mostly to being outside the EZ. If you try to block while on the floor, you're more likely to get low blocking penalties. Nothing in misconduct or gross misconduct (I'm reading the rules inbetween sentances here). Well, I can't find anything in the rules, if someone else can, let me know, otherwise I'm assuming that there are no penalties for repeatedly taking oneself out of play. The only thing you have to worry about is potentially tripping other people up.
TJ, you say "if you're not in play, you cannot score points", but 8.3 doesn't say that. I have no idea where you're getting this from. Please see the link I posted, the other refs are in agreement that being upright isn't a requirement to score points.
Del, sliding on one knee is legal as it's not adversely affecting gameplay, unless you trip someone while doing it.
I know you can't skate out of bounds to avoid a block, but I can't find anything anywhere about downing yourself to avoid a block.
You can try running on your knees, not sure how far you'll get though!