Thanks for the explanation karadoc.
Personally i prefer automove style in unmodded bts, in my opinion it make the game feels more fluid, but i think you know what the best for this mod though.
No. Just no. Objectively no.
It's never OK in a turn-based game, to have the game force units to take actions that cause them to suicide without the player having the opportunity to tell them not to suicide. Suicidal units are a bad thing and karadoc's change was a very important one. The vanilla mechanics were BUGGED when it comes to units moving into danger even as someone tried to interrupt them, please don't support bugs or adding them back

.
Panzers/SEALS are terrible in ancient starts; literally worthless in value-over-base because of how late they are. Adding flanking to the panzer would do almost nothing to cure its weakness.
Maybe if you gave the panzer 37 strength or the SEAL 28+ strength you might have something strong enough to actually be game-changing in the era it shows up. And yes, that would STILL leave them weaker than war chariot, immortal, prat, etc even though it sounds ridiculous. It's a comparable net str increase on a much later/less likely to have an impact unit. That late in the game, missiles, air power, massed collateral, gunships, and nukes all would allow even a basic faction to easily beat panzers anyway.
But instead, the panzers in default game are a laughably terrible 28 base str and in the majority of cases have equal utility to tanks. Waiting the longest out of ANY UU to get a benefit that's rarely realized! Fun! Flanking I helps but it doesn't even come close to addressing the disparity of the bonus that early units get + the advantage of having them early. It is actually LESS of an absolute advantage than the early units...though I can certainly see wanting to implement balance changes slowly.
I'm aware that giving panzers a STR boost will make them destroy anti-tanks and (briefly, very briefly) have no counter. I don't see an issue with that; people will know the threat is approaching and have to prepare by getting flight earlier (for fighters to soften them) or stocking up on arty. Considering how long you have to wait to use the units, it's perfectly reasonable that there is a window (preferably a decent one) where said units are difficult to stop.