Pros and cons to this issue.
take any animal only a few days old and hand rear it you will become mother, father, family
hand rear anything and it thinks its human.
yes he may still be shy but i doubt it. if you look at him as a wild mouse i see possible dieases? being from wild stock.
if you keep him id suggest a vet and vacc of some sort
mice are easy to keep and very friendly ive raised many *of course with mommah mouses help*
but ive experience with hand raising possums and wallabies:
from this size (54grams)
those are not my images just an example i have no copies of our raised babies.