The latest in a long, seemingly unending chain of MP-10 Masterpiece Convoy redecos has surfaced tonight on the
TFCLUB变形金刚联盟 Weibo page, and it's none other than the second Transformers Collaborative series entry. MP-10G is the Ghostbusters-themed Optimus Prime Ecto-35 Edition. This would be the "top secret" element that's been hidden on the IDW Ghostbusters/Transformers crossover miniseries connecting cover art since it was originally previewed - understandably, since there's very likely some official reveal event in the planning for this new Masterpiece Prime.
We can't say for sure at this point how many new elements there might be to this release, though we can clearly see that extra parts are present to outfit Roller as a giant ghost trap, and evidently MP-10G comes with its own Slimer figurine, much like Ectotron. What's more, there's conspicuous straps bound to the front panel of the box, and one end is rounded off. The rear panel of the box is sadly not shown, but if we were to guess, there might well be some unlicensed nuclear accelerator detailing back there, leaving the box designed to serve as a wearable proton pack backpack when the toy is removed. Or, if this is meant to debut at San Diego Comic Con - a possibility we really can't rule out at this point - maybe it's even meant to be a backpack while the toy is still inside, helping to spread out the burden of the day's haul.