My knee-jerk reaction is to say something about how a loose interpretation makes these abilities strictly better than a spell, what with metamagic feats etc.

The OSR junkie in me thinks that circumventing metamagic feats is A-OK, though. Viva la creativity!
Not sure what OSR means, but if you're spending a feat for an effect, it better be worthwhile.

Also, it doesn't give you much incentive to be better at grappling or tripping or hitting things if you can't move.