Well, of all the attempts to link G1 to G2, yours is undoubtedly the most successful. The last significant piece of information we received about the G1 storyline was that Velika was actually a Great Being; you seized upon that, as well as upon the plot lines of Marendar and of Voporak and the Mask of Time, which had been left unresolved, to carry Vakama and with him the reader from the last embers of G1 to the new beginning of G2.
The transition is more conceptual than physical. The events actually narrated in the epic are almost a background: the locations and the number of characters are reduced to a minimum, in no small part thanks to the appearance of Marendar, which not only kills all G1 characters (other than Vakama, Velika and Voporak), thus bringing their stories, and therefore most of the G1 storyline, to a close, but also simplifies the plot considerably, allowing us to concentrate on the interactions between a limited number of characters. The action is also extremely limited: the battle between Velika and Marendar is not, in my opinion, an essential part of the plot.
The central element of the epic is the concept of destiny, which lay at the heart of the G1 universe from the very start. Vakama is, at the beginning, still bound to a destiny which has been chosen for him by the Great Beings and thus allows Velika to control him. During the course of the epic, Vakama goes beyond that destiny, realizing that it is no longer a valid notion. He thus defies Velika and the Great Beings and eventually leaves his universe behind altogether, giving to the Toa Nui the task of creating a new one. The reader can see this mainly by analyzing the conversations and the visions (the descriptions of the visions are written superbly), whereas the action, as I said, merely serves as a background.
The aspect which I don't think you focused on enough are the Great Beings themselves. It is implied that Voporak and the Vahi are the key to their return, Velika talks about a last experiment and about the anomalous nature of Spherus Magna; none of these hints, however, is truly resolved. Of course, as I've said before, this epic develops a concept rather than a story and thus not everything needs to be explained for it to work. Still, I found the shift between the scene of the Great Beings' return and the next one too abrupt, leaving me with questions about the Great Beings' plans that are never answered.
I also think that in the last chapter you could have found a more explicit way to make the reader understand that the new island is actually Okoto; I understood, of course, and probably everyone else will as well, but still, entrusting that function to a mere link to your blog is not, I think, very appropriate.
That said, this was an extremely deep and enjoyable epic. It undoubtedly has a sense of closure about it, which is certainly in line with the current spirit of BZP and the forums, where we can all see that BIONICLE's sun is finally setting.