It would definitely make more thematic sense to put extra copies on top of your deck if discarding is unbalanced. I wanted extra copies to slip out of existence if there was no space, however placing in the near future could work as well.
I would think thematics before mechanics right? I really would prefer this card to maintain its "timed" theme without having to be too overpowered. Even if it means cost increases.
Is there really a thematic difference? When I envision a Time Slip, it is simply the manipulation of time to an uncontrolled point. Here it is when as many copies have been drawn from the deck. The issue, however, lies with the excess and how you want to approach it.
With your idea of bringing all copies to the top of the deck, that is quite strong, especially without drawing power, seeing as you've guaranteed almost dead draws for the next n turns if done so correctly, despite the quanta that would we generated in that time. However, this will not have much impact in the endgame when decks have waned in size...
If you do wish to maintain the effect as is, then the cost increase is evident. But I would still be concerned with how quickly, especially in upgraded play, this can be played and lockdown early draws.