eamon, I am intrigued... and a little confused.
Let me set up an example to see if I understand your system correctly.
UENT:
Player A hits Monster Z with a UENT daze. Player B then takes his turn. He also hits Monster Z with a UENT daze. Now the daze lasts till the end of Player B's turn, instead of Player A. Correct?
Save ends:
Again, Player A hits Monster Z with a daze (this time save ends). Player B then hits Monster Z with a daze (save ends). Monster Z takes its turn (but only has 1 action since it is dazed). At the end of the turn, it rolls 2 saves, one for each daze condition.
If it saves against both, it is no longer dazed.
If it saves against one, it is dazed and have to roll a single save next turn.
If it doesn't save against either, it is dazed and have to roll two saves next turn.
Correct?
Question: If you gain a save outside of your turn, under your house rule, is it only possible to save against one of the two daze conditions?
Thinking about it, it does make a little sense to have the roll on the inflictors turn. I often find that players more easily remember the conditions they put on the monsters than the conditions they themselves are afflicted by.
Also: Does the Warden change in any way then? I would assume not and they still roll an additional save at the beginning of their turn?
lwp also brings up delaying to prevent the save from happening. But this is already an issue with UENT (and I really can't remember how it is dealt with right now?).
Let me set up an example to see if I understand your system correctly.
UENT:
Player A hits Monster Z with a UENT daze. Player B then takes his turn. He also hits Monster Z with a UENT daze. Now the daze lasts till the end of Player B's turn, instead of Player A. Correct?
Save ends:
Again, Player A hits Monster Z with a daze (this time save ends). Player B then hits Monster Z with a daze (save ends). Monster Z takes its turn (but only has 1 action since it is dazed). At the end of the turn, it rolls 2 saves, one for each daze condition.
If it saves against both, it is no longer dazed.
If it saves against one, it is dazed and have to roll a single save next turn.
If it doesn't save against either, it is dazed and have to roll two saves next turn.
Correct?
Question: If you gain a save outside of your turn, under your house rule, is it only possible to save against one of the two daze conditions?
With the amount of bonus saves at higher levels, will save ends still end up better when rolled on the inflictors turn?You're right.
For my part, I think UENT is closer to the balance that the devs intended than (save ends). [Unless we're talking about elites and solos, but I won't get into that now.] UENT is basically "duration: 1 round," which allows everyone the opportunity to take advantage of a condition. It's simple and straightforward, so it's hard to imagine that it isn't exactly what the devs intended.
Unfortunately, UENT tracking is also one of the common complaints made by 4e gamers. If it weren't for those set-up powers you mention, I'd say "Screw it, saves are rolled during the target's turn!" As it is though, I don't want to reduce those powers to near-uselessness and I don't want to go through all the powers in the game to categorize them into 'party advantages' or 'character advantages.' I have a bit of free time, but not that much free time.
So I'm leaning toward 'saves are rolled during the inflictor's turn.' It's more to track, but we already track UENT conditions that way anyway. So I think it's the lesser of two evils.
Thinking about it, it does make a little sense to have the roll on the inflictors turn. I often find that players more easily remember the conditions they put on the monsters than the conditions they themselves are afflicted by.

Also: Does the Warden change in any way then? I would assume not and they still roll an additional save at the beginning of their turn?
lwp also brings up delaying to prevent the save from happening. But this is already an issue with UENT (and I really can't remember how it is dealt with right now?).