We currently use Semantic MediaWiki for knowledge management. I've been considering creating an extension for it to handle procedure writing, but as you said I can't imagine getting it perfect. I feel like it would always be somewhat of a hack.
As for "these procedures will be used once and then discarded": that's not really an issue. Most procedures would not be used just once, since we'd reference a procedure for installing hardware if we ever needed to remove it. Procedures used to fix something will be reused if it breaks again.
As for "these procedures will be used once and then discarded": that's not really an issue. Most procedures would not be used just once, since we'd reference a procedure for installing hardware if we ever needed to remove it. Procedures used to fix something will be reused if it breaks again.