That argument doesn’t really fly when Grail Knights are mounted knights.
If Kruber can be a Grail Knight then why shouldn’t Kerillian be a Sister of the Thorn, when they’re both cavalry units?
Besides, adding spells to her repertoire wouldn’t really step on Sienna’s role.
Sienna is a human wizard, her repertoire is already limited. Kerillian, as an elf, is a much more versatile potential caster.
Possible new weapons could be;
- Thrown javelin (Alternate fire; charge up, increases penetration)
- A “bolt” spell (like a rock flying at high speed; alternate fire is an explosive rock)
- A “burst” spell (Like a shower of thorns and acid spores; alternate fire creates a slow cloud of acid)
- A “beam trap” spell (Creates thorns on the ground, wraps enemies in thorns that slow and damage them; alternate fire summons a dryad)
These could all be added to her ranged weapon slot, and have alternate fire.