I can confirm that this happens, but I know this is by design; e.g. with AI the next in line assumes control over the squad, which is a MUST; with humans this happens normally too and makes sense, since ArmA is not always respawn by design.

I'm not sure if this could/should be solved by the mission maker. Then again it would be very sexy if this is an option if respawn is enabled. This makes this ticket rather a feature request, but to be treated as such, it would have to be rephrased entirely, including the additonal option for respawn modes.

Wait a minute, if respawn is set any playable units including ai can be in the group. Losing control to an A.I in an MP environment wrecks the mission.
This wasn't how it used to be. Back an engine version or so it was different.

Single Player functionality and multiplayer functionality requirements are very different.

The answer to all issues shouldn't be left to the mission maker to solve

You need to run an MP community to understand the effects this can have and none of it is positive.

If this was group respawn then it would be correct, but not for base respawn. It simply breaks the command and control.

That's how it always was. The mission maker has to make sure that the correct leader gets selected after respawn again.

Though this should finally get improved.

Edit: I guess it's related to rank and rating. If a second unit in the group has a higher rating and the same rank it'll be selected as leader when the leader dies. But like written, that's just a guess.