My experience putting together my own haggadah was a much more labor intensive process than I deemed at first. One of the most difficult aspects was how to artfully, and respectfully, deviate from the traditional text by adding certain passages in remembrance of the Master (after all, for disciples, this is a mitzvah, not an option). Entering into the world of creating liturgy is treading on hallowed ground. One should not be flippant or cavalier with how you “create” texts for worship.
One important factor I have discovered is not necessarily the need for more texts (though I have them), but more importantly, having a distinctively Messianic kavanah for the texts that are already there. Kavanah is basically defined as the intention one has behind the prayers as you are reciting them. Different traditions within Judaism pray the same prayers, but will sometimes have different kavanot behind them.
As a disciple, a very profound way to connect with the traditional seder is to have a Yeshua-centered kavanah behind sections of the haggadah. One area in particular I have found this to be most profound is in the Hallel psalms. Singing these psalms with thoughts of the Master’s death, burial, and resurrection in mind brings these praises a completely different layer of meaning for us who call him Messiah.
In so doing, I think we have a great opportunity to connect with the Master, without thinking we have to invent so much new material.