No, not a silly idea, you just need a low-loft batting. Soft & Crafty or Poly-Fil are both good options as long as you don't plan to put any lit candles on top of the tablecloth. I've used Poly-Fil to make placemats & it quilts up nicely and is relatively flat. It gives very little stitch definition, but the only way to get more is to go with a higher loft & you don't want that for a tablecloth. If you want your stitches to really show, try a contrasting thread and/or either a 28wt or 40wt thread. Also, make sure there is roughly the same amount of quilting across the quilt as poly batting will bunch in the wash if it has somewhere else to go.
Can't wait to see what you come up with! Some of my favorite quilts are wholecloth.