The Episode I Battle Droids have all subsequent versions beaten in terms of plastic quality, but they aren't correctly proportioned. Their thighs are too thick and the eyes/optical receptors are misplaced on the BD's head.
The first BD that was done in the proper proportions was the POTJ Security Battle Droid, which for the most part was also done in a decent quality of plastic (hence why I think it could and should be reissued given the reappearance of that class of BD in ROTS). The POTJ Boomer Damage BD was also of the correct proportions, but the plastic on it was a little bit lower quality than the Security version.
All subsequent BDs have been properly proportioned and film accurate/CG model, well, on-model, with the exception of the ROTS BD's eyes/optics being misplaced back to the Episode I placement, but as we all know, the plastic quality, as Groundskeeper Willie would say, is "SHITE!"
I'd love to see decent quality plastic Battle Droids with Episode I level or beyond articulation but post-POTJ level proportions. Hell, do an SA version with a removable backpack and make intentional variants of blue, red, yellow, and plain colors.
I'm also going on record as saying I want a film accurate Destroyer Droid that, while not necessarily transforming, uses the superior Episode I body and the post-Saga head, and has a clear deflector shield that covers it.