If you don't want the back-and-forth anymore, then you can write it simply in this way:
When you play THIS, any opponent may pay 5 life. If a player does, he takes control of THIS.
I already addressed this issue. I do not want a triggered or activated ability because I don't want it Stifled or Trickbinded. I am aware that the chances of that happening are slim to none, but I don't want to leave that option open.
I feel it rather weak this way, however; i liked the life bid for the tutor.
The problem with the life bid tutor is that your opponent is always at the disadvantage. You can see this in the example I provided in the first post.
What about something like Chain of Vapor?
(do the demonic). Then an opponent of your choice may pay 5 life. If the player does, he or she may copy this spell.
Well there have been previous Demonic Tutor rehashes which look something like : You and target opponent {do a demonic}. This would be the same with the exception of your opponent having to pay 5 life for it.
This means a lot. Not only do you get to the search for your card, but your opponent just put himself into closer Tendrils range in combo.