Thoughts on OD&D Thieves

The Thief. 

Is the Thief a specialist, weak and awkward in physical combat like a wizard? Or is the Thief a agile rogue capable of holding her own in combat like a cleric? Supplement I seems to indicate the Thief is a scholar of sorts , a specialist in legerdemain and chicanery. One who has dedicated themselves to the skills of the cutpurse, burglar, and engineering to the the exclusion of  physical training. This is reflected in the d4 hit dice, and using the same combat chart as the magic user. Gygax seems to be saying a first level Thief has less skill than a normal man in combat. Later editions of the game have a different conception of the thief, seeing them as at least equal to a cleric in physical combat, with improved hit charts and d6 hit dice. Making them more akin to a shadowy assassin or ninja than the weak and flabby scholar of Supplement I.  

So how does one square the Thief's climbing and back stab ability with the d4 hit dice and weak hit charts? There seems to be an incongruity here. Surely the ability to scale sheer walls and make precise strikes with a blade are contrary to the assumption of the physical capabilities of the Thief as indicated by hit dice and attack matrix. Unless a Thief's skill is supernatural. If the Thief's skills are magical , beyond what is possible by other classes or men then the hit dice/attack matrix are acceptable. The Thief has otherworldly powers to rely on, the practice of which, or the dedication to , somehow exclude the possibility of physical training. 

This conception of the Thief is very different than what is usually thought of the class. It has the benefit of encouraging other classes to attempt Thief like abilities ( this is in line with Old School Play, where traps should be disarmed by narrative rather than rolling, and everyone has occasion to be sneaky.) 

If the idea that the Thief is using some dark magical force to sneak, back stab, hide, and climb walls is unacceptable. I suggest bumping the Thief to the Cleric attack matrix, and rolling d6 for hit dice, This makes them the dangerous rogue of later editions, relying on agility and physical skill to adventure, be sure to adjust XP accordingly. (Suggest Median between existing Thief and Cleric XP tables.)