I would simply suggest a nice mega range shimano or sachs FW and shimano RD and the shifting will be as good or better than he is used to.
if he does not mind loosing some of the top end you could always find something like a 15-30 FW and maybe that will work on the current RD
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk