Doing the relic properties now, there are a few things you should be aware of.
Infect - 1/2 + Absorb Poison (you get this way too late in the game)
I don't think this will actually work, I've never tried it before though.
Well, you'd have to find an enemy to test it on. AFAIK, the hack claims that absorb+weak = 2x healing from the magic attack.. I figure absorb+1/2 = 1/2 healing from the magic attack. See how the Elemental relic fares with it on and off (Elemental has 1/2 and absorb for Poison).
Nuke - ignore Mblock
Meteor - ignore Mblock
Flare - 1/2 Fire and/or 1/2 Wind and/or ignore MBlock
You do realize this is now ignores evasion right? The evade patch fixes this, this is the sniper sight property, it's used on the lucky ring.
Hmm, do you have a better suggestion? There's nothing else I can think of that would be the equivalent of unblockable. The Lucky Ring would be more useful simply due to stat boosts. The only next best suggestion is to use the increase magic damage option, but no equipment uses that I think...
Tornado - null Wind and/or resist Weak + once weak, always weak
Cure+Life spells - add Weak status
I don't know why you want these to resist/give weak (Near Fatal) status, it doesn't actually do anything except make the character crouch down all the time, pretty pointless.
I was thinking more desperation attack chances.
Scan - 1/2 all elementals (the idea is to remove all weaknesses on yourself)
This seems way too overpowered, unless you get this one later in the game.
It replaces the Ribbon's treasure chests.. one @ Locke's scenario with the hidden treasure.. and the WOR Narshe treasure (Rune Edge -> Ribbon).. and maybe a few more...
The only other method is the Coliseum.
The closest equivalent item is the Unidentified Relic from stealing it from the Ice Rider.. and you can get plenty more on the Veldt. The difference is that the Unidentified has the built-in Exp Egg and the other evasion/mblock reductions...
Imp - resist Imp
How about also having it give a nice defense boost while the character wearing it is an imp? I don't know when you get it so I'm not sure what would be good.
That's thinking outside of the box. How dare you!

This replaces the Gauntlet. The earliest you get this is @ Banon's hideout

and two more I think in the WOR.. one @ Umaro's cave and one @ Kefka's Tower. You can definately get more via the Coliseum.
Slow2 - prevent back attack
You mean the run from side attacks option the back guard usually has?
Yes.
Rasp - (if it didn't have the HP/MP boosts.. or in addition to those boosts) adding one of the MP reduction options
I think the boosts are enough.
Oh well.
Going back a few pages, when you had JCE's monster use broken desperation attacks, did you confuse it or something? Looking at its script it should just be attacking and using its special, those attacks are only set for its control and rage commands.
Did you see the movie? That should answer your question in a nutshell. IIRC, the monster command list in the Coliseum uses the Control command set.