Have not done this with olive but Junipers are frequently used to make 'phoenix graft' or 'Tanuki' trees using a dead wood base and younger trees attached. Usually the trunk of the live plant is embedded into a groove in the dead wood so as it ggrows iit appears to be a single live vein of wood on a larger dead trunk.
Search 'phoenix graft' or 'tanuki' for lots of online inspiration.
I would avoid threading live sections through holes. A live branch growing from a dead section with no obvious connection to roots will not look natural and as the branch thickens inside the hole circulation will eventually be cut and it will almost certainly die.
Another option is to us the stump as a 'rocky mountain' and plant smaller trees in pockets of soil so they appear to be trees growing on a steep cliff.
Don't underestimate the care needed to maintain such a planting. Watering becomes critical as not only does the tree use water and evaporation takes some but the porous wood will also soak even more water away from the root pockets and evaporate it even faster into the surrounding air. Rock plantings have similar problems and require much more water than similar trees in pots to keep the trees alive.
Search for inspiration for rock plantings but ignore the more common root over rock entries. Here's one from Bonsai Empire:
https://www.bonsaiempire.com/basics/styling/rock-planting
