i read yesterday, that someone had done testing on this, and apparently the respawn into group, looks for a group member to respawn into ON DEATH, not on respawn.
So you could do 1 of 2 things.
a) Start with an additional unit in your group at the start of the mission, place the unit somewhere safe, and then when you die, setpos this unit to your respawn location
Use the above system to create another ai on your death at the safe location, and you will always have an ai to spawn into
Until you stop creating ai on your respawn count.
or
b) add a "Hit" event handler to your player, have tyhis create an ai for you, incorporate a check, so that you only have one created ai at any one time
hit eventhandler should be triggered before you die and therefore there will be an ai in your group prior to your death.
I would run with the first option