Earl at centre may be a stupid idea, but is it any more stupid than having to line up a 10 - 12 combo using 2 of the 3 diminuitive fly halves in the matchday squad should something happen to Dingwall?
With 6 back rows in the 23 and the backs replacement being specialist scrum and fly halves, any injuries among numbers 12 - 15 on the day will require rejigging the lineup in an unorthodox and profoundly sub-optimal manner. Earl to centre could well be the least worst option.