If Secret Invasion leaves the battlefield before its triggered ability resolves, the target creature won't be exiled and the enchanted creature won't become a copy of the target creature
By playing Jim, Space Traveler when you have the RLS Legacy in hand youll have spent five ink to play a four willpower and four health character that quests for two, a four-cost location, spent three ink to move Jim, Space Traveler there, and given Jim, Space Traveler is Evasive for as long as the RLS Legacy remains on the field - thats an absolutely wild amount of value if you can set it up for turn five
Casting it and immediately exiling a threat is strong, and you can follow that up with more mana or cards and life
Assuming its turn three, you can now swing in with your Kiln Fiend, protect it with Force of Negation, Lightning Bolt either the blocking creature or the opponent, and then cast Temur Battle Rage to do up to twenty-three damage depending on other blockers and whatnot