I suppose we could still use it as a Greater Snake Staff, rather than waste the Wizard Wars staff, but I've no clue what such a staff would do - save make bigger snakes... Dunno if I could use the snake model as some sorta astral projection attack that whips out from the staff and bites things.
If you want an honest opinion, i think you should stick with the summoning theme for the greater version. If it's called a "Greater Snake Staff", i think it would make sense for the staff to focus on summoning snakes to help you in battle. The meele part could act as a bite from a snake, so it applies poison that scales based on your affliction level, making it a strong poison at X level requirement and being a weak poison at earlier levels. The snakes themselves could also use upgrades based on your SC level, similiar to the undead summons. Making the snakes slightly stronger and different from low to mid and high tiers, with some proper scaling in usefullness for each tier. Could even go as far as adding a passive effect that helps the player and the enemy at the sametime, something like "You get poisoned from summoning a dark snake!", said poison can spread to nearby enemies, making them receive more damage from all sources for a moment, this also applies to the player, all enemies will deal increased damage for a moment.
Making it yet another affliction spell based staff would be redundant, more so when dark staff is somewhat recent and decent in its own way. Chances would be that this staff would become useless if it was offensive spell oriented, as we already have one staff of that kind in the same field. I know some people might disagree on this and want "NEW DAMAGING SPELLS NAO!!1!1!One" in the form of a new staff (i somewhat agree on the part of new spells, but in this case it's not the best approach), but honestly, the chances that the item will be of any use if that happens are pretty slim, i would rather see it as an utility weapon of sorts, like a support-role kind of thing and i think summons+passives are a decent approach to the item and players who want to experience something new (being closer to an actual summoner). This is all based on the currently existing spell oriented staves we have ingame, both fire and ice staves are lame and useless, unless you use potions to make them stronger, which nobody will bother with since there are much better elemental items available and one of the two staves has limitations to how you can use it (the meteor stuff, it's logical but it's also a massive downgrade to the item).
EDIT: Just had another idea for a passive effect, an aura similiar to the holy lance, that buffs the snakes for its duration, that are touching the aura. Might not be a bad idea, it's something new and summoner oriented.