I love the infinite respec for a regular playthrough, but would wholeheartedly endorse a much stricter version for tactician mode.
Would make no difference, all that players would do os change the difficulty before respeccing.
True enough, but if you're testing yourself to see how you do in tactician, then you're only cheating yourself, right? If you are going for the Tactician game completion achievement I'm pretty sure you can't change the difficulty anywhere along the way.
