Summoner… combat technique?? Instead: Unstable Summons.

[The Revanchist]

Didn't I recommend something earlier...?

ePerhaps, if the Summon fails to die before it "expires", you lose your hold on it? This would probably be nullified by the Summon Control, which could even be a reason to actually get it.

There it is!
Specifically, the Summoning Augmentation tree being capable of essentially nullifying the threat.

[Theyleon]

Have to agree with those above - this would turn into a tree which would be totally ignored by anyone who knew what they were doing - if these summons are powerful enough to be 'worth' the downside, they'd be too dangerous to risk having them turn on you.

[Delmuir]

Theyleon,
I don't disagree with your assessment, which is why I think their power should be augmented by being dependent upon a synergy with other summons.

If said summon were to turn on you, it'd be weaker alone than it would have been in your party. Thus, it be worth having in your party but not quite as powerful alone.