Ah, good news, I am sorry but I did mix up some arguments to the address_space_config struct. It makes sense now, no need for core team to do anything here, I just need to understand what I am doing better.
The VME64 standard introduces some new concepts such as the A40 adressing also available for single connector boards by combining the A24 (A1-A23) and D16 (D0-D15) lines where the latter are multiplexed with A24-A39 addresslines. Life is never simple... there is also an optional Configuration ROM capability defined. I think I leave the VME64 extension for later too.
I am still curious if the use of an extra addresspace to map the VME boards makes sense. In theory the Address modifiers adds and extra 8 address bits makin it possible to address 2^40 bytes of data also in a VME32 system. So maybe I can just use that approach and map the whole thing into a A40 address space in AS_PROGRAM?