Impedance Matching and Large Trace Widths
You don't have to worry about the impedance of very short PCB traces as part of a longer trace.  So you will have a thinner trace directly next to the chip.  But if the trace has to go any distance, then you need to adjust the thickness of the trace as it gets away from the chip.  You will just "fan out" the trace width away from the chip.  That is how I have always seen it done.

This is not unlike the connectors of any transmission line.  The impedance of a single short element might be a little less, but it is slight when compared to the overall transmission line.