If he gave up all rights wouldn’t that get weird on the pre-MM stuff again though?
You mean in terms of the way things are now, or are you talking about a hypothetical scenario where MP rejoined the band?
Either way, the answer is no.
At the time of MP's departure, DT, as a business enterprise, presumably had three primary sources of revenue: (1) record sales; (2) touring; and (3) merchandise. There are LOTS of ways things could have been set up, but lets say there were three corporations: (1) DT Enterprises, Inc.; (2) DT Touring, Inc.; and (3) DT Merchandising, Inc. (I'm obviously just making up names). And lets assume that, as of August 2010, each corporation had five shareholders (JM, JP, JR, JLB and MP), each of whom owned a 20% interest. DT Enterprises would have the contract with the record company that obligates it to produce X number of albums over the course of Y number of years, and the record company provides financial consideration based in part of sales. DT Touring contracts for concerts and receives income from promoters. DT Merchandising handles merchandise and receives revenue from sales.
Publishing income is separate, and I assume each individual member has a company to which he has assigned publishing rights and which handles the collection of publishing revenue via ASCAP, BMI, etc. and also from the record companies (possibly via DT Enterprises). Once MP left, there were two primary possibilities. The first is that he gives up all decision making rights in connection with all of the corporations but retains the right to receive distributions on an ongoing basis for product he was involved with. That's messy for a lot of reasons, not the least of which is that it carries the potential for regular, intrusive auditing. The second possibility is that some accountant figures out the likely present value of MP's future income stream, and the band entities pay him that amount of money for a full relinquishing of rights. In other words, MP gets a big chunk of cash, and the band has no future obligations to him. It's much cleaner, and I think that's what most bands do unless they don't have the cash for a buyout.
But let's assume there was a buyout and then MP rejoins. First of all, they probably have to go through the same exercise with MM because my understanding is that he became a "full member" of the band (as opposed to someone like Scott Travis in Judas Priest who, despite being the band's drummer longer than all other drummers combined, is only a contract employee). Then as for MP going forward, all you have to do is account separately for new album sales, which is easy since each album (and other recorded product) is typically accounted for separately. MP gets a share of new stuff but not of any sales of product prior to the rejoin. Touring is obviously simple, and merchandise can be structured in a similar way to record sales.
Needless to say, there's a lot of hypothetical and speculation there, but it's not something that's terribly difficult or awkward.
I voted "Other", that is the very first meeting inside the practice room at Berklee.
I would imagine seeing JP and JM first approach MP in the lunch room might be more interesting in terms of conversation, unless you're talking about them jamming together, and even then I doubt it was all that impressive.
I'm thinking about the very first jam's end, when/if they realised there was special chemistry at play. I'd love to catch those looks they gave each other.
I think those would all be interesting, but there are a lot of moments there -- probably relatively few of them all that interesting on their own, but being a fly on the wall for all of their time at Berklee would be pretty cool. Use your time machine to go back and take the place of a professor who tries to steer JP away from rock/metal and into jazz or who tries to convince MP that JM is toxic and that he shouldn't want anything to do with him or, on the day that JP and JM first noticed MP, directs the two Johns away from that room so that they never see MP practicing. Sorry...got carried away there.