Can I include just one or two S.H.I.E.L.D. supports from aspects other than my chosen aspect in my Maria Hill deck?

No, Maria Hill’s ability is all or nothing. You must include the maximum number of copies of each of exactly three S.H.I.E.L.D. supports from aspects other than your chosen aspect, or else you cannot have any S.H.I.E.L.D. supports from other aspects in your deck.