Hey mate,
I have a mono blue paper illusion deck IRL so I'm happy to see other people still appreciating my sweet teddy bears
Just one advice, though,
Unsettled mariner is ... useless here. Most of your illusions
disappear when targeted. That means that your oponent may TARGET your creature with spell, ignore the mariner cost, get countered, and your illusion will be still destroyed, because the countered spell targeted it.
Lord of the illusion gives tchem hexproof anyway and your main plan should be to copy it with
phantasmal image, and theb the mariners counter ability won't be needed anymore anyway.
As for my subjective approach to illusions, I found out that mixing tchem with too much control is sub-efficient. When I had control-ish approach to my illusions I usually ran out of steam pretty fast, and the illusions lack some additional traits to tchem to pose a threat. Like, merfolks have many additional abilities, islandwalks, counters, draws... Zombies have deathctouch, undying, menace. Illusions sometimes have hexproff and can grow large but that's pretty much it. They lack elasticity.
After some experimenting I found out they works best as a tempo / midrange deck.
I personally use
grand architect with tchem to make my illusions bigger and give me additional mana for spells like
steel hellkite or wurmcoild engine. Or
vedalken shackles. Combined with creatures like
Glen Elendra Archmage,
phyrexian metamorph and some utility cards that are a good target for
phantasmal image (in case the opponent is wary of your
lord of the unreal combo) you can make some funny synergies.
Do whatever you like with those suggestions, think about tchem or ignore tchem, whatever you like, I'm just sharing some thoughts. And have my like, Illusions were my first deck, I have it since about 15 years, so it's really nostalgic for me when I see them. Go illusions!