so i don't have much experience with grafting in general, but i would think that these vines would graft easily. i had something (bug?) once girdle the bark round one of my vines, something that would kill a tree, but it healed just fine. i have also had branches break, no so cleanly, where there is only a small strip of wood and bark joining the branch to the rest of the plant, and i put the pieces back together and bound them with wire & tape- took about a month to heal, not 100%, but the branch was joined and growing new leaves.
oh, and i am pretty sure, the pics of mature vines that are not entirely round and have lobes to the diameter, are actually multiple branches that have spun around each other, and when this happens, the vines' bark eventually fuses. the inner wood should condense, and likely fuse as well.
this is all with one individual plant healing & fusing with itself
i have had different caapi plants attempt to do this with each other, but i always pull them apart.... what happens when two different vines grow in proximity in the wild?
can two different individual caapi vines fuse? what about caapi, and another trees it grows up/through/on?
my real question, though, is why would you want to do this, what would you expect to gain, as far as "plant fitness"? typically, when i think of grafting to rootstock, i think of tasty fruits that have been grafted to avoid root-pathogens, or to increase cold (possibly drought) tolerance.
caapi & muricata etc seem to all grow pretty fast, both pretty cold sensitive, neither have tasty fruit, i don't think anyone is really investigating with any seriousness the pathogens of these plants....
i think you could probably do it, but would you be able to notice any difference? i guess there's only one way to find out!