A greatsword would be considered a bulky item in some systems so, yeah, encumbrance absolutely could come into play. And if you add the spell focus thing or the possibility of spell failure that might be considered more fair, right?
And of course there's verisimilitude to consider. Things get damaged and break sometimes (especially if they're not maintained properly), and they can be repaired. Why shouldn't that happen in the game? And who says that wouldn't be fun to experience? For me stuff like increases my immersion and as a martial lets me show off my versatility.