Sorry, can't fit all those auras into one item, and you can't change how the auras work either. You can, however, cheat a little bit
Turn all those auras into UNIT abilities (instead of item). Then, create a spellbook ability, and add all of those auras into the spellbook. Make sure the base order ID doesn't conflict with any other spellbook abilities you might have. Also, make sure the Min and Max Spells fields both equal the number of auras you have in the spellbook (in your case i guess it would be 8).
EDIT: btw, the original Spellbook ability is an item ability, make sure you change your dummy aura spellbook to a unit ability.
Make a trigger at map initialization that does Player - Disable <Spellbook Ability> for any player that could possibly own a unit that could use your aura item.
Then, create a trigger with Event - Unit picks up Item (or something like that) and Conditions - Item Typed of <Manipulated Item> is equal to <Aura Item>. For the actions, have Add <Spellbook Ability> to <Triggering Unit>.
Then, create another trigger that removes the spellbook ability when a unit drops the aura item (event - unit drops item, etc.).
Basically, you are adding your auras which would be on your item if they could all fit into a disabled spellbook ability. It's disabled so that the spellbook ability icon doesn't show up on the UI. However, the auras themselves (inside the spellbook) are not disabled so they still have all their effects. So every time a unit picks up the item, the spellbook ability is added (and with it all the auras) and whenever a unit drops the item, the ability (and all the auras) are removed. Somebody playing the game won't be able to tell the difference
IMPORTANT: if you have an inventory like Backpack in melee maps, where a unit can pick up an item but can't use the item's effects, make sure to put conditions in your triggers that check to see whether or not the triggering unit has the right kind of inventory ability(yes inventories are actually abilities).