I think you could do this - but you would need to redraw/recalculate the seam allowances. If the template includes them but they aren't already marked, draw them in at 1/4". Then enlarge. Then redraw the seam allowances to be 1/4" again and cut your templates that size.
For a King size - what overall size are you thinking? My batting is 120x120, so let's assume your King is 100x100. You probably want 10 to 12 blocks across and down, for lots of pattern repetition - so 10" maybe. No bigger than that. 8 or 9" might be better.