I dont see a reason for a rule that says "you have to fight to death".
You should be allowed to withdraw from a fight if you wish.
For example, when i got attacked in my fighter with a RH BS while carrying a full load on nomad superior brains. I didnt want to be destroyed (It took me a lot of effort to get all those nomad SB), so i withdraw when my shield generator was destroyed.
Restricting access to a system after you are destroyed is a common practice between factions. But the contendants have to agree the terms before the fight.
As an example, i found lancer once in AW space (during the last AW SDF war), i asked him to leave, he refused so i engaged him. After defeating him, he agreed to leave AW space. He could had said "no" instead, and run from me. but he didnt.
The chance of leaving is actually in use. Before attacking, is usually considered polite asking to leave (If faction wars), or asking money/goods (if pirate), or ask the other for a duel.
(If you find any mistake in my English, please let me know via a PM)
(Really, I speak terrible English, so please, tell me if I make mistakes. I'd like to improve it a bit )