I would personally say hard no, or at least hard no until the next gen comes out. Pokemon has been around for many years now and each new gen brings another layer of complexity to the game that the main games do a horrible job of capturing. It is one of the reasons why I personally love reborn and rejuvenation so much. However, this can be a double edged sword. Pokemon's complexity was slowly introduced through each gen, however, that complexity can be daunting to those just picking up the games now (if they are playing more competitively, of course). However, changing the rules to the game (whether that be adding or removing features) can seriously annoy long time players.
Pokemon is actually the very reason why I am so hesitant to try any other 'pokemon-esque' games or heavily edited pokemon fangames. The very idea of having to re-learn all the mechanics, names, types, stats, moves, abilities, items, etc; is a bit daunting. Lots of time is invested into learning these mechanics and the idea of going to a 'pokemon-esque' game / pokemon fangame with their own brand new mechanics that need to be relearned from the ground up is a bit of a turn off for me personally.
Personally, I will admit that pokemon fangames with non-cannon pokemon, abilities, items, and moves to be rather aggravating. As it is a pokemon fangame, the idea is that the player will in fact be playing pokemon. I enjoy being able to explore the game and use the mechanics GF has introduced. Especially because the games they make often never give you a reason to use them. But the addition of non-cannon mechanics means that non-cannon strategies will be used. This often makes me feel like I am learning a useless skill. Non-cannon mechanics also mean the official sites are now void and fangames often do not have websites or properly updated forums going into detail to discuss the changes. Rejuvenation already requires that I have multiple guides / mechanic pages open at all times: Natures, Pokemon Moves, IV/EV focus, current Pokemon Location Guide, current Item Location Guide, (occasionally) current Walkthrough, and the Field Effects Guide. My computer is chuggin already, opening up more guides for new fakemon (which are currently in the game) and updated movepools, mechanics, and abilities; will kill it for sure.
Jokes aside, I do not view all new changes as negative. While I am not a big fan of fakemon, I absolutely LOVE the field effects system in both reborn and rejuvenation. The field effects can be confusing and absolutely maddening in some areas, but I simply love their addition.
So with all that being said, I will mostly agree with what everyone else is saying. Arceus is a spin off. Balance wise, I do not think it is a bad idea, but we do not know what changes will be made in the new gen coming out this fall. If it is not added in the newest gen, any mechanic changes made now could conflict with the changes GF introduces. If frostbite is not introduced in the newest gen, I cannot see frostbite being properly implemented without new moves/abilities being created, entire movepools/abilities being restructured, and all current battles/team comps being redesigned with this new status affect in mind. All these changes will be added on top of the (possible) mechanic changes GF introduces in this next gen.
That is my 2 cents on the matter.