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The "simple" way Excel intends to offer consists of a multi-column ComboBox where one column is shown in the drop-down and another used to fill the linked cell. However, when I consider that you will have to store the values for the two columns somewhere the idea you outline would seem to be not more complicated.
It all burns down to a definition of "simple". In the attached workbook I created two overlapping named ranges, Index and Dropdown, where Dropdown is in the first column of Index. This setup supports VLOOKUP. INDEX/MATCH won't require that (columns could be in any sequence). The setup for a ComboBox would look pretty much the same.
I pointed the cell validation in C3 to the Dropdown range and used the different lookups in column A.
=INDEX(Index,MATCH(C3,Dropdown,0),2)
and
=VLOOKUP(C3,Index,2,FALSE)