Admittedly I don't really know what could have changed to have a pretty comparable situation to our timeline to have George Thomas in major field command in the east, but let's for the sake of argument assume (makes nice with Grant, Butler dies, some other stuff) this were the case. How would George Thomas being in command of the army of the James at the beginning of the overland campaign change the war, if at all?
Of course in our timeline the army of the James failed miserably under the command of Benjamin Butler, maneuvering themselves into a hopeless bottleneck at Bermuda Hundred and basically taking away any shot of diverting manpower from Northern Virginia. In this situation we have an extremely capable commander in Thomas in charge, so I'm just asking out of curiosity more than anything what difference this would've made, if any