That should be scripts, not plug ins, as this is Ace, not MV.
You will probably need a script if you want the player to lose and still have 1HP. As long as the player has some HP, no matter how little, the engine assumes that they have not lost.
An alternative would be to inflict the immortal state at the beginning, and have the dialogue on the troop event page, set to the condition of 0HP. If you still need that 1HP, you can add it at the end of the dialogue.
However, a bit more detail would probably get you a better answer, in that you haven't said what, if anything, you want to happen after the dialogue. Is the player to be transferred to a particular place? Does the game over then get triggered? Something else? Does the immortal state remain, or is it then removed so that the player dies?