DHs who never played the field are the equivalent of a D-/D- first baseman. so he will be very bad at 1B. if you move him to OF you get the out of position penalty plus another penalty for moving to a more difficult spot on the defensive spectrum, so he will disastrously bad in the OF.
to give you an idea of how bad, in a 1978 progressive i played Rico Carty in RF for 989 innings. he made 30 errors with another 20 minus range plays, for an 0.832 fielding percentage. try to avoid doing this.
you cannot make the starting pitcher the DH in a DH league, it wont let you. if you don't have anyone in the DH slot (because you traded away or demoted to AAA your starting DH and didn't reset the lineup) the sim will choose position players over pitchers to fill the spot. i believe it is possible to get a pitcher who is not the starting pitcher to be the DH, but you would need to have the DH spot empty, all other position players on rest or fatigued below their auto rest, and even then it might just use someone fatigued.
so basically that theme idea won't work.