Auras you put on other players' creatures are a little bit harder to remember, Mind Control effects are harder to play than normal, and cards which search your opponent's deck (like, say, Praetor's Grasp) are nightmares to resolve
Dont hold back
Holon Mentor and Holon Legacy both fit well within the Holon engine model of building decks, as did the energy spread that included Holon Energy FF, Holon Energy GL, Holon Energy WP, as well as Boost Energy, Scramble Energy, and Rainbow Energy
You'll want to mill your opponents to force their most powerful cards into their graveyard, which Dimir specializes in and also works if you want to go with a Rogue theme
Still, good tutors always see extensive play, and even if it gets relegated to Commander and nowhere else, the demand should keep the price fairly high.
Deadly Rollick Free spells have always been and will always be absurdly good because they ignore the most basic balancing mechanism in Magic: To affect the board, you must spend mana