Thresh is beefy all in support champion and he should function like other tank supports and that's why he should buy relic shield for increased tankiness helping him to all in. He is a diver but a tanky diver unlike rakan who's more like skirmisher cause he goes in and gets back out. Having to last hit my botttom lane partener minions is incredibly frosteighting for both since many times we end losing the cs and not of ng the cold. Ancient coin is for the passive healing and shielding champions(soraka-janna-nami) not for the tanky engage ones who want to play agressive and tarde a lot in lane and for that reason sustain is needed. However thresh is ranged and he can't take the full advantage of relic shield in the laning phase. To fix that u need to classify champions to each specific role(skirmishers-divers-juggernauts-healers e.t.c) more visible to the people, in other words when the go to the champion pool they will be able to see the classes of champions to each specific role and understand and memorise the specialisation of each champion that has acertain role. Then u could make relic shield available to melee champions but also to the diver class in general(where thresh kicks in) with a difference to the ranged divers-the will execute minions like melee champions below 75% hp if they walk to 125 range. That way thresh will take full advantage of the relic shield without making other champions(like sona or janna) broken. Can this plz be done? Thresh already is a niche pico in solo queau and i truly enjoy playing him and i hate that relic shield doesn't fit propertly onto his playstyle.
Anther way to make thresh use relic shield is to make him melee witch is the last thought cause it will destroy some of the strengths and uniqueness of the champion.
Disclaimer: this article is not only about how ranged divers like thresh can make use of relic shield but how ranged divers can take full advantage of a any melee item(knight's vow-sterak's gage-frozen malet).