Let's say your freshman congressman still gets to pick two committees. But he gets to serve on one for six years and the other for four years, at which point he must chose something else. There is precedent for committee term limits. The House Budget, Ethics and Intelligence committees have term limits, all for specialized reasons-for example, no one would serve on the Ethics Committee if they had to stay there permanently. There is a bad element to this idea.
Legislators develop expertise in a few subject areas through long service on a committee.
That expertise would be lost. The gain in breadth would at least equal the loss in depth. Legislators rely chiefly on staff for depth anyhow. It is breadth that the legislator is supposed to bring to the job. The seniority system wouldn't change much under committee term limits.