Suppose that after the Panay and Nanking incidents and seeing what was going on in Munich in late '38, the Army and Navy got together (truce, I suppose) and decided to do a little brainstorming on how to help Plan Orange along when (not IF) it was needed. The more Navy-Marine-centric Pacific team gets a little squirrelly on the Army's contribution, and decides to go down the path of involving more Colored combat formations, specially overseas. Sometime in mid '39, the 9th and 10th Cavalry Rgts are rotated to the PI, greeted by the Scouts, and given an intense tour of the terrain features of Luzon. They then train, with the Scouts, to become something of an "OPFOR" type unit, simulating an invading force, call themselves the "Pajanese", maybe. Existing white non-coastal defense formations train against them, rotate back to CONUS and are replaced by newly raised units that train against the Paj. Additional Colored units are raised in the US, they rotate to the PI, train, replace some of the prior deployed battalions, who rotate back to the US to serve as cadre for standing up a new formation, call it the 2nd Cavalry Division. Some of these units of 2nd Cav are deployed piecemeal to seemingly backwater Pacific locations where they replace/eliminate the need for the Marine Defense Battalions, allowing those units to train in the PI against the accursed Paj before returning to the US to cadre new Marine formations. 2nd Cav replaces the rotated units, yadda, yadda, yadda, lather, rinse, repeat. You get the idea.
Hopefully, you can get in a few iterations of this before the manure contacts the rotary air mover, allowing a PI defense that's about the same size as in real life, but, much batter trained, and, reinforced by a roughly division size former OPFOR outfit. I know, I know, won't work if Mac's around...so have him fallen off a horse and kicked in the head when he's out showing off with the new guys. The horseshoe lobotomy works so well that he sneaks out of the hospital one day while in the grasp of a major delusion, wanders into the hills, and is never seen again (CONUS hospital to boot)...happy now? The invading Japanese are severely frustrated by the defensive prowess of all the PI's defenders, but really hate facing the "Night Fighters". Stories get back to the US as the invaders are stung by the occasional defeat and the pain of a large number of Pyrrhic victories; Eleanor Roosevelt goes into high gear...
Whoops, how'd I miss that...need to say this makes a start on 2 problems; stiffens the defense of the PI, and, advances the effective utilization of non-whites in combat arms. There...