Exegete:
There’s no reason that someone couldn’t be an altar server and a reader (or acolyte and lector) at the same Mass.
This is actually mentioned somewhere in the GIRM I think. However, I know that I’ve read it. It is emphasizes that we are supposed to use two lay readers (when there isn’t an Instituted Lector) and that readers may not serve at the altar.
However, I know that many parishes break this all the time… A number of parishes use only 1 reader instead of 2, and some (usually during daily mass) have one person serve as reader, altar server and EMHC in one mass.
I don’t have time to look this up, however, I know this was written down.