I would currently recommend against playing dead civs because raiding is broken for them (you can send them out, but they then remain in limbo indefinitely).
However, dead civs are hard to get because the accounting is bugged, so civs that should be dead (no members for 1000 year, no sites, etc.) usually are still treated as struggling (unlimited migrant waves, monarch, caravan, snotty pointy-ears demanding you stop cutting trees). The only sure way to check if a civ is dead is to embark and check the civ screen's civ sub screen. If it's completely empty the civ is dead. If the dwarven civ is listed it's not. The dwarven civ gets added when another civ is encountered officially for dead civs, though.
Dead civs are also culled from the list of playable civs if there is at least one that isn't dead, so even if they actually do die they won't be available. This doesn't matter in your case, as you don't want any dorfs around at all.
I've given up on dead civs for the time being and am currently blessed with a civ that has a monarch at the mountainhome (and not spewing mandates at my fortress). I have to deal with tree quotas and nobles (you still get a mayor even for dead civs, though), and get the dwarven caravan, but I can live with that.
I've got a couple of scripts for pushing civs that should die over the brink during worldgen and entering dead ones in the list of civs you can play as, respectively, but I suggest waiting unless you don't care about raiding (and having somewhere other than exile to send all the dorfs that crumble due to stress). The scripts, should you still want to play a dead civ, can be found here:
https://github.com/PatrikLundell/scripts/tree/own_scripts. Note that the script pages are web pages with the scripts on them, not script files. The two scripts are "slabciv" and "permit_dead".