The following could happen:
You get hit by a super effective move before you manage to set up, killing Shedinja of.
Forest Curse turns you into a Grass type, meaning you will be weak to Fire, Bug, Ice, Poison, Flying, Fighting and Fairy moves, so once one of those hit you your Shedinja gets killed of.
Your opponent use a status move like Toxic, killing Shedinja of (if you manage to pull of the Recycle you'll run out of PP eventually)
Your opponent summons Hail/Sandstorm, killing Shedinja of.
Your opponent uses a phasing moves, then uses a entry hazard, killing Shedinja.
Your opponent have a Pokemon with Mold Breaker use any move, killing Shedinja.
Your opponent also hacks his Pokemon so that it could use all the aforementioned strategies, killing Shedinja of.
Your opponent let you set up, and you kill his/hers entire team.
Overall there are just to many things that can go wrong for this illegal Shedinja set to be remotely viable. The biggest flaw is that Forest Curse makes you a Grass type, not a Ghost type, meaning this strategy will actually allow more attacks to hit and kill you. The set is a gimmick that won't yield and spectacular result, but might work against really inexperienced trainers.