Yeah, people do survive such things (I survived a broken neck without any paralysis, getting really lucky there), but there are many things the critical table doesn't (can't) take into consideration: such as numerous secondary and tertiary effects from getting hurt (like infections and/or the panic that may result), so a lot of that will still be up to the GM to interpret. At the very least, as you mention, they will not be able to survive on their own and need much care, depending upon the level of the group (and the current situation), perhaps more care than the other characters are able to provide. There are high level spells that heal nerve damage, but getting to such a healer could be a problem. I just thought of something: this could be a great divine intervention moment, especially if there is a plot thread you really want the group to tug on. (Of course, it could also be the opposite of divine intervention...)
Also, about the unconsciousness, it is entirely possible that he would not pass out. So he could be laying there awake, able to hear and see everything going on, but unable to act. Very scary, imo.
I totally get you about playing such a character, only in very certain situations can it be at all enjoyable. I once played in a Shadowrun 3rd Ed game of "high-power" where my friend played a magician who was a quadriplegic, but because he could just go astral, and his mental stats were very high his astral form was a monster, and he could still cast spells and summon really tough spirits, he was a super power unto himself basically. (The GM was totally unprepared for a high-power game.)