Subject: B1-X Battle Droid
Status: Fanon
Capsule:

20 years after the B1 saw failure at Naboo, and 10 after the B2 debuted at Geonosis, Baktoid Automata decided it was time for the next upgrade in it's line of infantry droids.
The niche had had it's problems for sometimes now. The B1 was stupid and flimsy, hardly worth its cheap cost. The B2, although more agressive and stronger, still paled in comparison to clone troopers. Droidekas, B3s, and Scorponeks were better served as assault fighters and weapons platforms.
The new model then was a hybrid. Years ago, the BX-series droid commando was the top of the line when it came to automated commando units. While not quite the par with their opposite Clone Commandos, they were still quite a threatening face on the field. The problem? Expensive, more than 20x the value of a B2, and 100x the value of a B1.
That has since changed, however. The B1-X is nearly identical to the B1 aesthetically, except with reinforced armor, similar in hardiness to the BX-commando. While it does lack some of the finer infiltration software, it featured a modern version of the BX-series combat programming and enough tactical and battle training to make it the equivalant of a Carida graduate.
Better yet, the B1-X is considerably cheaper than the BX; years of research and refinement have made the B1-X nearly as cheap to produce now, as the B1 was to produce in 22 BBY. Combined with their programming, heavy armor, and their weapons (including new E-6 Blaster Rifles, SE-15 Blaster Pistol, stun batons, and grenades), the B1-X is the thing Republic soldiers now fear.
Of course there are downsides. The B1-X is a tad larger than the B1, meaning ships can carry fewer of them. They're still vulnerable to headshots and EMPs, and are the most expensive infantry units in the CIS.
Even still, factories across Confederate space are cranking these babies out by the millions each day.