I remember somebody bringing it up once before, Tehya1, but I don't recall which thread. I just spent about thirty minutes scanning through the 'archived I&S' subforum but I didn't find it there. I scanned the active thread titles but nothing popped as the one I read it in.
All of that is to say that I didn't see an active thread with the rollover suggestion, so if you wanted to put one up, I don't think you'd be duplicating anything 'under discussion' or waiting for the OP to call for a vote.
The second idea about the time boosters being applied before you start production would need to be in a separate thread since it is a different mechanic - and I haven't seen that one mentioned previously. I'm also unclear on that concept, but that could be my inadequate language skills again. It sounds like you want to be able to drop the timers before you've set the production but I don't understand how that would resolve losing the time since the building can only produce at the quantity-time set. Even for barracks, the quantity is based on my armories and possibly AWs. I've got five slots. I set for maximum possible production of... let's say archers. So, it takes around 6 hours, 40 minutes at my current production rate.
Is what you're wanting to cut down on the number of times you click the "x" from the time boosts screen, click to train more archers, click the time button, select the timer boost, etc.? You want to drop in 10 hours worth of boosts in advance so you just keep clicking on the archers until it finally stays in the window? Because that's the only way I see that I'd know the boosts had run out.
If I've understood that correctly, then how would that be possible with a rollover for time not used in place? It would read it as time not used since nothing had been produced before applying the timer, wouldn't it? And then it would produce a ten-hour time booster, to resolve the rollover to keep from wasting unused production time?