Nice to see a solid Nin deck such as this. I can tell this is pretty well oiled and has seen a lot of play time! I hope you don't mind that I link to it in my primer as I am trying to provide options to folks looking at different ways to build Izzet.
I know you mentioned that you don't want to be much more competitive. I am curious as to where you draw the line here as I find people's take on what is competitive and what is casual to be extremely subjective and relative to their playgroup and their own builds. Others just want to play certain pet cards or combos. That said, I do have a few thoughts. Take em or leave em.
at 3.49 your mana curve is a bit on the high side I would say for a non-green deck even with all the artifact ramp. In izzet, I really hate getting high cost cards in my opening hands as it seems to really bog down the deck and kill the fun factor. Without very many looting effects, I see this as being even more of issue for you. Getting that average cmc below 3.0 should make the deck run more smoothly. Just my 2 cents.
On this vein, both the Nivs kind of stick out to me as being inefficient for the effect. Your build strikes me as a deck that typically wants to turn creatures sideways to get damage through. Something like
Chasm Skulker or
The Locust God look to me as being great fits and worth the cost, while the Nivs seem out of place in an otherwise very focused deck.
I did want to discuss two main points with you about the deck:
1.
Targets for Nin's ability. Without too much creature recursion in Izzet colors, you are looking at either pinging your own creatures with Nin that A. don't mind dying like
Solemn Simulacrum B. Indestructible or immune creatures like
Darksteel Myr or
Stuffy Doll. or C. Stealing your opponent's creatures and killing them.
Is there a reason you aren't leaning more into the creature theft route?
2.
Mana issues in activating Nin She strikes me as being a very mana intensive commander in a color combo that can struggle with generating mana resources. I generally view Nin's ability as being akin to a draw X spell. IMO in these colors we just don't have access to the kind of mana it takes for these spells to be very worthwhile or efficient in terms of actually drawing cards. There are simply more efficient options. Adding green or even black would allow us to make better use of that X cost. Purely Izzet needs to be able to copy this ability to make the most use out of it or double the draw with a draw multiplier
Teferi's Ageless Insight. In the case of Nin you can also double the damage that the ability does by using something like
Furnace of Rath.
Training Grounds for Nin seems pretty solid especially if you have a way to untap her.
Rings of Brighthearth serves a similar function to
illusionist's bracers
Some specific cards to consider:
Dockside Extortionist seems like auto-include. I know it's pricey but you have the ability to copy it.
Dramatic Reversal,
Turnabout - untapping your resources seems like a pretty solid strategy with Nin
Vedalken Shackles - repeatable theft seems good
Darksteel Plate - makes any creature into a
Darksteel Myr inlcuding Nin herself.
Battle Hymn - could be a really solid way to get some explosive mana.
Burnished Hart,
Dreamscape Artist,
Neheb, Dreadhorde Champion,
Treasonous Ogre - creatures that generate mana are probably going to be ideal for a deck like this I would think.
Clever Impersonator - looks like one of the more solid and efficient copy spells.
Coastal Piracy,
Reconnaissance Mission,
Keep Watch,
Distant Melody and
Bident of Thassa all seem like solid considerations for creature based card draw.
Nezahal, Primal Tide seems like a fun card even though it costs 7! He (she?) is an investment that can protect itself and draw a ton of cards in a multiplayer setting.
Ominous Seas might be pretty fun and an efficient way to gain a scary board position.
Basilisk Collar - in a more creature heavy deck as this, I could see you getting some use out of it. Lifegain in Izzet colors can be a welcome thing. With Nin, all your pings are now lethal.
After all this, I am realizing maybe I want to build this deck too, lol! Fun stuff!!