Question about the weapons on other characters...

[Terra Blade]

So I like that I can take a character normally specialized in one weapon and have them use another. However if we can't access weapon skills, how viable is this as an option for character customization in the long run? Will there be ways to unlock weapons training for characters so they can get the full benefit of the weapon either now or in the future? Or is there a mechanic I haven't unlocked/figured out yet?

[Elveone]

All weapons can be equipped by all characters and weapon skills are tied to the individual weapon used and have nothing to do with the character. There are weapon masteries but those are tied to specific way of playing the weapon or to stats and all characters have weapon masteries for all weapon types.

[Mr. Blue Sky]

As mentioned, all characters can use all weapons with no penalty. In fact, some character abilities are tweaked slightly to account for the weapon you have (e.g. Wingrave's Righteous Strike is a wide horizontal swing if wielding a melee weapon, or a long-range forward stab if wielding a ranged weapon). When the game refers to a weapon skill, it is referring to the special ability specific to that individual weapon, like Ransom's retreating shotgun blast or Nightshade's full-auto magazine. Every character class (Warmaster, Survivalist, Arcanist) unlocks unique mastery passive bonuses specific to each weapon type (Guardian [sword-and-shield], Executioner [two-handers], Twin Striker [dual daggers], Marksman [guns]) as you unlock more talent ranks; you can find them in the accolade talents tab in the Talents page. All this is to say there is no drawback for giving a character a new weapon. Your Wayfinder AND weapon combination will inform much of the cadence of your play style and will be one of your most important gameplay choices.

To be clear, some characters do have certain preferences based on the nature of their kit that may influence how suitable a weapon type is for them. For example, Venomess's Master of Venoms passive rewards multiple weapon hits, as each individual hit applies a Venom stack, so you likely want fast-attacking weapons like burst rifles such as Nightshade or any twin daggers. Similarly, Grendel's Blood Rage passive hinges on breaking an enemy's guard, so he might want a Breaker [2H axe/mace] or shotgun.

In summary, all Wayfinders are specialized in all weapons simultaneously, so there is no penalty or additional training required for any Wayfinder to pick up any given weapon. Certain Wayfinders may have rough preferences, but there is ultimately nothing stopping you from giving any weapon to any Wayfinder. If you want Silo to swing a greatsword or Niss to snipe with a runecannon, do it. You may find a surprisingly interesting play style that works for you.