Ironically Nick wasn't worried about being affected by timeslipping himself as an elf his lifespan was pretty much infinite but the problem came in the form of the ingredients as well as what effect it would have on him. Obviously the ingredients would crumble away and render the trip pointless but even further Nick himself would end up fully matured which would also render the trip pointless as only someone with maturing magic could undergo the ceremony. Nick had easily thought of a few possible ideas that might work to fix these problems but each one was horribly difficult.-
For example he could rebuild the drones he had gotten from the dwemer ruin as time had little effect on the things while they were active thus meaning the timeslipping wouldn't cause any trouble for them. At that point he merely needed to find a way to isolate and purge the temporal energies that would try and affect the ingredients the drones would collect for him and he would be able to collect whatever he wanted from history without issue. As should be obvious however if he had such a mastery of time magic then he wouldn't have this issue to begin with and gaining that sort of mastery was no easy feat.-
In fact doing so was probably more difficult than creating a whole new realm once again. The thing about realm creation from what Nick could see was that you don't need much mastery over the fundamental forces of one such as time and space. Rather you actually only need a tiny amount of each of these forces power to be combined correctly in order to create an incomplete realm like what Nick currently had. From there it is merely a matter of adding more and more of these forces power to the realm to expand it and complete it into a full world.-
The fact was that there was no real need for mastery of these forces in order to create a realm but merely resources. On the flip side however if one wanted to create an entire world instantly then mastery was required to do so. That was how Celebrimbors world had been born after all as the Ainur and Valar were born with absolute mastery of their respective forces and elements that sang the song of creation that fused that mastery into a full blown world from the start.-
In fact these beings could be considered gods that were born with these domains innately and used them to create that world. For one of them to manipulate the forces of time should they have that domain would be easy but Nick was no god nor did he possess any inkling of that domain. It was ironically very easy to determine what domains one was generally attuned to just by seeing what sort of magics they are most talented at. Nicks domains for example would be crafting , souls , fire , lightning , weather , birds , languages and magic.-
To clarify having a domain of magic didn't refer to magic in general but rather magical energy or mana. All in all Nicks domains were varied and wide reaching but had very clear distinctions between them. In the same vein Dumbledore had the domains of fire , alchemy and magic from what Nick knew of the man. It should be clarified that having more domains didn't necessarily mean more powerful as in fact the opposite was normally true. Having fewer domains meant far less time and effort to elevate ones understanding and mastery of their domains to a higher level.-
Where Nick had to separate his energy between eight domains Dumbledore split his between three or possibly four so he obviously had much faster progress in them than Nick did. Or at least that would be the case if Nick wasn't cheating by having a system that let him have access to resources Dumbledore had no hope of matching , books on subjects from other worlds , materials from other worlds , crafting methods and styles from other worlds and all of the same things from this one. There was a vast gap between the resources available to each of them and it showed as Nick was rapidly catching up to the old man while the old goat could only rely on his own effort and severely limited resources to improve himself.-
Needless to say if Nick didn't have the system his own growth would probably slow down to around the same level as the old goats if perhaps a little faster due to the knowledge and skill he already possessed. Anyway Nick had nowhere near the amount of mastery required to snatch the ingredients from the past which left him little choice beyond sucking it up and shelling out the points the system gouges for the ingredients he couldn't get through the vampires.