External dependencies linking multiple projects

I am about to go to P3, but perhaps some of you know how to do what I need in MSP?

I am managing a software/hardware/network development/integration project with about 16 subprojects from various vendors and subsystem providers. Creating the inter-project links has been extremely difficult and not at all reliable in MSP. After much investigation it seems that if the MSP ghost does not show up (that is if the task ID# is missing (assigned to the ghost), but there is no way to get the ghost to display (no matter how many times one expands and collapses the summaries above it)), the scheduler does not recognize the link, regardless of the presence of the link text in the "Successor" column. Needless to say, the schedules are inaccurate.

Is there a fix to this? A workaround? Something I dont know about multiple inserted subprojects?

Is this kind of a thing easier with P3, as they tell me?

The project is about 3K lines total, os it isnt large, but it has a very aggressive sched and lots of attn from above.