The two objective stumbling blocks would be the failure to use holocomms when all our heroes always do massive amounts of communicating, and the failure to consider cloaks as a tactical possibility when the two main enemies, Romulans and Klingons, have both been shown dabbling in this key technology previously (even if retroactively).
Holocomms are a nuance. Cloaks are a real nuisance. Again because nowhere in Trek but "Balance of Terror" is the idea put forth that invisibility or visual stealth would be a new thing - indeed, all sorts of advanced aliens are practicing it all the time. So why does it take our heroes by surprise both when the Romulans do it in TOS, and when the Klingons do it in "The Vulcan Hello"? Although the latter offense is much lesser, as nobody pretends invisibility would be "theoretical" or unheard of. It's just deemed an unlikely option for Klingons, even if with unduly harsh words.
Timo Saloniemi
