Such conditions and inducements as Alan enunerates as to the enlistments of ex-confederates in the Union Army seemed to only apply to Steele's Army in Little Rock and maybe up in the Northwest around Fayetteville. In the outposts garrisons Pine Bluff enlistments were different. It was more uncivilized in Southeast arkansas for the reason that I have stated above. Any ablebodied man that was around ran for the brushes anytime any patrol, Union or Confederate, was in the area. Ever think of why? Every ablebodied man in Jefferson county had already been enlisted into the Confederate Army in 1862 because of war fever or the Conscription act so any able bodied males in Jefferson county in 1864 stuck out like a sore thumb. The high percentage was that these men were A.W.O.L.'s, for whatever reason, from the Confederate army in the first place.
I can not condeam any southerner for joining the Union army in order to survive and provide for his family. But the question is, what were the conditions that caused the people to do that in the first place? Most of the civilians and soldiers who had returned home simply wanted no part in the war and wanted to just be left alone by both side.
I don't find much evidence that many of these defections were for a change of heart and "Loyality to the Union" except for those who opposed the secession in the first place. It was kind of like Confederate P.O.W. becoming "galvanized Yankee's" to get out of prisons up north. Most of that idea of 'change of heart', seems to be from researcher projecting themselves into the minds of those enlistees and wanting to say "OH, they must have seen the Light and come to salvation by joining the Federals".
In my mind even if their enlisting was for the inducements, it was more a matter of survival than any other reason.