Hm… Could you do two different Revisions of the same part? But even then, they’d have to tell you which one they really want when placing the order. Unless they are discontinuing the first one, if so, you can just remove your FG0000 from the cross reference and add FG0001.
Randy is right. The slightly difference, makes it a different part and if you do not want to deal with revisions, your customer should provide you a different partid as a reference. Otherwise, you do not know which of the two to produce.
We do not use it, but maybe using the Alternate method of production could be an option?
(I am not sure… if this works with same rev… )