OK, keep in mind first post newb here, but I have a question as well.
What about a layered approach as follows?
This would be done inside a tube structure like copper pipe cap or whatever as an outer shell, followed by layers.........................
1) non-conductive powder of choice, just thick enough to cover the chips and make a "level" surface and provide good contact with all the components on the board(s)
2)thin layer of thermal adhesive like AA quickly followed by.........
3) a interference/press fitted cylindrical heat-sink pushing it all together tightly.
Of coarse all "holes" would have to be sealed to keep the powder in.
What I am thinking is the powder would readily fill all the spaces around the odd shaped components and allow for us to get back to a flat surface area to apply a heat-sink with minimal use of the more expensive epoxy.
Surely with the powder compressed, and "sealed" by the layer of AA it would still help with vibration damage.
Another good thing, assuming this would work, you could carefully cut it open and extract the board(s) at a later date and the powder would be easy to clean off of since it wont adhere to them.
Again, sorry if the idea is seriously flawwed, I am just getting into all this and have much to learn I'm sure.
Jim