Here's one. OBR, using a DH. In the 7th inning the coach comes out and wants to bat the pitcher for the second baseman, and put any future pitcher in that spot in the batting order.
I know if the DH comes into the game on defense the pitcher bats in the spot of the defensive player who leaves the game, but this coach wanted to make the switch while they were on offense. Legal?

From BRD 2004 item 67: OBR: The pitcher may pinch hit only for the DH. PENALTY: Point not covered. OFF INTERP 48-67: FITZPATRICK: If the pitcher bats for anyone other than the DH: When appealed properly, the pitcher is an improper batter. The proper batter is out and removed from the game. The pitcher will continue to bat in the spot of the replaced player, and the new defensive player hits in the DH spot. The role of the DH is terminated whenever the infraction is discovered.

DG, your reference is absolutely correct however, read it carefully. I think what is left out of the original thread is that someone will have to replace the second baseman. If the pitcher is staying on the mound, that someone has to be the DH. Now in accordance with 6.10 b, this is allowed and in essence the result will be what the second half of BRD Item 67 states.

We used to do the same thing when we had a good hitting pitcher and it was late in the game. we would remove a weak hitter but good defensive player. The DH role is terminated.

I don't have all my references with me but, I believe what happened was legal.

I think the OFF INTERP is saying "when appealed properly, the pitcher is an improper batter". 6.10b allows for the double switch you mention: "Designated hitter may be used defensively, continuing to bat in the same position in the batting order, but the pitcher must then bat in the place of the substituted defensive player". But what is described in the post is a projected substitution since DH has not taken the field defensively yet. When you used to do this, did you do it while the pitcher was on the mound, or to start an inning on defense?