If you need a slot, I think
Ghirapur Orrery would be a good option, since it could help your opponents way more than you.
Greatsword could be replaced with
Loxodon Warhammer. same CMC but you also get trample and
lifelink.
Deathrender could also be replaced. the effect is nice, but you're lacking scary creatures that could be cheated in with it and 6 mana for +2/+2 is to expensive.
Then I've taken a look for some other equipments:
O-NaginataVulshok BattlegearBarbed BattlegearSword of Kaldracurrent equipments that could be replaced:
Ogre's Cleaver (cmc 7 for +5/+0, I've mentioned more cost efficient options above)
Worldslayer (very conditional, since you need stuff like
Darksteel Plate to make real use of it and you lack of tutors to make this a consistent win condition)
Btw, the important numbers for the power of your commander are 7, 11 and 21 (3, 2 or 1 hit in order to kill someone with commander damage). the numbers in between aren't that important since they tend to produce overkill damage.