Can there be a way to get wither skulls without relaying on other mods like tinckers?

U could enchant the sword with looting III.

Thats still a 5.5% chance and tinkers give you a better drop rate then looting 3

There already is. Just farm wither skeletons with the mob grinder. Currently you will need another mod to spawn them but i will be bringing back the spawner soon.