In an somewhat recent interview with Creative Director Rich Lambert, this ancient request was briefly addressed. As you can see, one of the most obvious and important issues with adding a new weapon skill line, supposedly, is the colossal amount of artwork that this would require.
https://wccftech.com/elder-scrolls-online-shadow-over-morrowind-qa-creative-director-talks-necrom-chapter-community-requests/
Of course, the statement is correct in context. But there is something unaddressed here.
For most people, we ask for new weapons not necessarily because we want new in-game models, but because we want variety, novelty and more identity added to combat. That being said, there are definitely ways to work around this issue while still achieving our goal.
The gap: in ESO, it’s possible to wield a single weapon in one hand and nothing on the other one. It’s also possible to wield nothing on both hands. This, however, has no impact on how you play, and it’s only a cripple for the player.
We can fill this gap.
- Throwable daggers and axes, wielded on one hand only, could conserve existent artwork, while adding a new skill line cleverly. Art-wise, this would only require new animations for the skills and new VFX (a given).
- A grimoire/scroll could be either 2-handed or 1-handed. A book/scroll logically wouldn’t use the same materials as other weapons, so we could even get a new crafting station. It could actually reuse existent artwork in the game as well.
- Spell on your hands, skyrim-style. Or runes in the air too. No need for any new weapons, though it would require new animations, obviously, and a new spell system in order to equip them.
- Martial arts. Again, no new weapons required, other than maybe simplified and standardized knuckles for some flavour. Of course, the animations could be more demanding, but not necessarily. If we drew from the air bender archetype (wind magic does exist in the TES universe), this could even end up similar to how Overcharge (the sorcerer ultimate) already works in game.
- Finally, restoration staff models can be reused for a new type of staff (alteration, illusion, mysticism?) and make a Protection skill line, same as Destruction staves which share a same asset for different types of effects. Alternatively, we could even split all these staves into separate skill lines, as many have suggested before in order to balance frost staves better.
Respectfully, I think that it's clear this is not the main challenge to adding new weapons. The community has been long asking for new skill lines, yet the main problem mentioned by the developers does not really seem to be a true barrier. Thus, I ask for more transparency, as it feels that there's an actual design decision behind the lack of new skill lines which is not being talked about.