Riverdusk

I assume by ice/ice you mean ice/cold? Both are good sets and with the combo you'd be on the stronger side of the control scale as well as one of the best at helping take down AV's and Giant Monsters thanks to infrigidate, benumb, sleet, and heat loss and good buffs to teammates. Only warning I'd have is ice (along with earth) is probably the weakest damage of any of the control sets. So solo would be a rough go. Fantastic combo if you like to team though. Ice/storm is another option that might work for your concept? It would give you more damage, but the buffs and debuffs aren't as good. So that would be the tradeoff.

I've run up probably half dozen characters so far into the 20's or close to it and by level 22 I've always gotten at least one rare salvage drop (usually 2 or 3). Simple sell at the auction house for close to a million inf each. Easily covers the cost of SO's at level 22 and/or to start dipping into standard IO's instead. Maybe running at a full +100% exp rate you'll get unlucky and not get a rare drop by 22? Might happen, but would be unusual from what I've experienced.

Just curious if anyone knows why controllers don't have access to the "minimal Fx" version of Cold Domination, and yet defenders and corruptors do? One of the reasons I never played the set for long in the past was because of the ice shields turning your whole party into ugly Jack Frost clones. Maybe it is minor to some people, but it just annoyed me too much. It is nice defenders and corruptors have the option around that now, but controllers still don't. Would be nice to see.

Most important long term goal in an illusion build in my experience is getting enough recharge to get phantom army up full time or very close to it at least. They pretty much take care of both your damage and defense for you (as they are very good at keeping the mobs attention with a built in taunt effect). You'll be able to solo any high level content you want at that point including any AV I ever tried. My experience was with both illusion/rad and illusion/dark. /time from what I can see is just as powerful and should make the recharge goal even easier.

Plant/trap sounds really good. Confuse everything then safely go in and set your traps to finish them off.

Keep in mind katana is pretty much a carbon copy of broadsword but superior damage over time. There are still reasons to go broadsword of course just for personal preference (or wanting to pair it with shield), but if you are going for efficiency, katana would be the better route.