so i was thinking back about this post.
fresh!error would be absolutely terrifying.
being possessed by fresh is already a nightmare in of itself. but then error - this guy is just dealing with the little parasite living in his eye socket now, making him do things he can't control while conscious. for someone like error who doesn't like touch, who needs some sense of control - this even more torturous. and there's a high likelihood fresh wouldn't be let go of if error technically can't really die and his form is stable with fresh's influence.
and then the fresh side. he wants to spread his parasites around. he's already scary enough. what can he do when he has strings? directly transfer his parasites to the potential hosts? (like maybe the strings hold someone's soul and the little parasites crawl down it to the new host) he wouldn't have to worry about short range anymore. though maybe he would have error's visual struggles.
it would be freshmagedon all over again
now, one potential i think might hold off freshmagedon is how long fresh would stay possessing error. if fresh starts to gain emotions the longer he stays in a host, staying in error for too long amount of a time may become overwhelming which would make him need to exit before he starts feeling bad about what he's doing. in this case, the main parasite would be vulnerable enough for error to finally eradicate. now... this would mean that there might be an infestation error comes back to but perhaps he would be able to clean up most of the trash. be like the one time he wants help from other anomalies (so maybe ink and killer would be the most likely to be able to assist since ink in most cases wouldn't have anything for the parasite to attach to and killer's soul is weird enough with the player's influence and also being outside the body that it isn't particularly something fresh would want to risk).
which then this could pose a war against the freshes after the multiverse has seen what fresh may be capable of so they end up trying to capture or get rid of in some way any remaining parasites to avoid the multiverse from falling into 90's possession. which that would just put a target on every parasites' back instead of being able to keep the facade of being generally harmless.
so actually maybe it wouldn't be a tactical advantage to possess error in most cases and would more just risk the long game and would probably only be an option if he were backed into a corner.