As Paul has mentioned this is a limitation in the AU standard. If you want this changed then write to Apple to ask for it, or ask them to make Logic compatible with the VST standard. It would be a better to get this sorted at the source rather than expecting VSL to provide a workaround.
It is entirely possible to load multiple instances of VEP - I've seen composers using 9 instances with no problems. Doing it this way also helps for organisation as you can split your sections into instances, which can make it easier to find the instruments when you want to edit them.
M