I like it, but IMO it can be improved. Dropping certain Gishkis like Mind Augus and Gustkraken during the opponent's turn can be a sweet disruptive play, since they have on-Summon effects. Bonus points if you are activating "Forbidden Arts of the Gishki". I also appreciate that it makes you activate the Ritual Spell normally, so there should be little conflicts with timings and rulings involved in Ritual Summoning during the opponent's turn as an pseudo-Quick Effect. Finally, I appreciate as well that the GY effect doesn't have any 1-turn stun of any sort and thus can be used right away after getting it in the GY by discarding it, milling it, etc.
As for improvements, for starters IMO I see no reason for it to not grab Gishkis with Levels lower than 4. That way it would be able to grab Gishki Vision. Another improvement is giving it a name that makes it searchable, since AFAIK non-Ritual Gishki Spell/Traps don't have anything that searches them.
May include the Giskhi Spell/Trap stuff in another card, but this is already an ambitious first step, yes?