I see, and I understand that with the help of some of us lagooners, you would take into consideration to (let us) set up a new forum, (let us) transfer the content of this forum to the new one as far as technically possible, and then drop this forum.
I say "as far as possible", because not everything might be transferred e.g., for the moment I do not see any possibility to transfer the PMs to a new forum without having a proper database dump, and if this "disappearing posts" error proves to be severe, also not all of the posts might be found (retrouvées) in the depths of the lagoon. But maybe, transferring PMs is not so critical, and posts that have disappeared today in this forum do not make the new forum worse than this one is

. We will have to make a complete list of everything we want to transfer, and then test the transferrability of each item on the list, so that we come up with a complete documentation of what is technically transferrable.
And as (I think)
luke pointed out some time ago: when the new forum is operational, the old forum can be closed for new contributions, but left alive in "read only" mode for some time until the transit is clearly complete and stable.
If you want us to "get to business" with this work, it needs a clear commitment from your side, an official "Let's go!" so that we can set up the project, divide the work and start with the migration.
It would also need some work from your side, especially for you I see here
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Overall project governance = you are the boss, and you have the last word for every major decision, especially strategic, legal and economic decisions.
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Design and concept of the new Forum = at least regarding my own design capabilities, nobody really wants to have a "designed by qbv8" forum, believe me

And for the overall concept I think that we can work this out together with a team of knowledgeable lagooners.
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Legal issues = This comprises the "behavioral rules" of the forum as well as possible copyright issues regarding design elements like smileys, graphics, etc. But this should be not a big problem for you, as you have already solved this in the past.
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Marketing issues = everything concerning advertisements in this forum including contracts, etc. Here the same is true as before: you have already gone through this so that it should as well not be such a big problem.
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Strategic decisions = This concerns e.g. the decision whether we want to start this migration project, it requires choosing the provider, and deciding on the base system we use for the new forum (e.g. phpBB or something else). For both questions we can do the preparatory work, compile the necessary information and provide you with a suggestion agreed upon within the technical crew, such that you are then able to make your decision.
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Financials = This of course is closely related to the advertisements and to the contracts with the server provider, and that is clearly your matter.
So far my point of view.
Oh yes, and in case I did not make it clear before: I am volunteering to help.
Best regards,
qbv8