Hmmm dunno if thats a good idea - it would reduce the amount of options avalaible for each Demigod. It also means each DG will be more alike as they will have to get one helmt/boots/ring etc. etc. and late game every DG will have the best of each. With the way it is now, all the Demigods are allowed to use any items they want and so choose lots of different playstyles. E.G. with Regulus you can go pure snipe/mine/mark of betrayal which means you have to get lots of mana items. Or, you can go angel damage build meaning you will max on damage/hp+armour. This would not be viable if each DG could only get one of each item
about some builds that take a lot of mana i believe it will make them a bit more difficult since u must thing when to use them not like now that u can just spam them mindlesly if u have 2 helms.Some builds will be viable but it wont be so easy since u cant just be able to use spells all time without any mana problem, some spells imo shouldnt be always active like angel fury, u must use it at the right time not all in all game,
Also this will stop in a degree huge health demigods, i played a game as tb vs angel regulus, and i won because i used 2 helmets and the just bought only armor and had 6k hp and almost 50% armor
Now for some weaknesses of demigods can be shadowed by items, and then have almost no weaknesses.
buying best item it will not be so easy expect if enemy demigods die all the time
the only other option is max stats but i dont know if it easy to be implented, This will be the easy solution but not 100% good. Max stats is the 100% imo