I've managed to keep a fort going through multiple sieges without any exotic corpse disposal, just a 10z dump and an atom smasher. Essentially you have to be really careful about everything else.
- Make sure to flag high stress-propensity dwarves on arrival and keep them away from battlefields.
- Make sure there is always booze, is a well, is a legendary dining room, that they can replace worn clothes with really nice ones... really, to the best of your ability, make darn sure the battlefield is the ONLY thing stressing them.
- Make sure you military is satisfying their needs instead of "individual combat drilling" their way to the brink of madness. To do this with the least micromanagement possible, exploit the fact that on-duty dwarves ignore burrow restrictions. Designate the ENTIRE map, from the sky to the magma sea, as a burrow. Then cut the barracks out of that burrow. That way, unless they are scheduled to train, your military will not go in there.
- After a battle make sure corpse disposal is an absolute priority and use this process:
1. Designate the entire battlefield for dumping.
2. Go into stocks (make sure your bookkeeper is set to highest precision) and un-forbid corpses and body parts.
3. Make sure everything gets to the garbage dump. A dropped ear on the main stairwell is a disaster in the making. The trick here is to make sure every corpse-bit goes directly to the trash to minimize exposure.
- Finally, it takes a bit of active management for when a dwarf gets high stress. I automatically exile/terminate any Dwarf who is haggard, oblivious, or committing acts of violence. However, it is possible to stabilize a dwarf who is not doing... great. In my last for I had one live with a flashing red arrow for over five years; he never quite got un-stressed but I kept him from falling apart.