Questions:
[*] Interdiction is and always was a thing in the Elite universe. Clearly this is how a lot of fights are going to start.
[*] How would you intend to call for help from your friends? (Assuming they're not travelling with you)
Friend setting. When a friend is interdicted, you get a message
[*] How would you expect them to be able to target you?
They hyperjump right next to you, if within range of their jump engine. You are the nav beacon. Can be there in 10 seconds?
[*] How long would you expect it to take for them to turn up to assist?
10 seconds ish, from call to decision, to frameshift charge and jump
[*] If your friends weren't nearby, what would you do?
You're on your own, or general distress call. Requires more comms stuff - maybe can only call to friends?
[*] Would you expect to be able to chat with them in-game if they're outside of the system?
Yes, within limits. What about local cluster chat? I know that breaks some rules of Elite, but there you go. You either dive into MMO to make it more fun or have it alone and sterile.
[*] If so, how would you expect that to work?
what about a comms unit, that can be upgraded? level 1 is same system, level 10 is 10 systems away. Maybe the systems would have hyperspace units whizzing back and forth to send comms FTL.
[*] Would you expect to be able to voice chat or just text?
voice within system, text from without.
[*] Let's assume your friends are out-of-system, some tens of Light Years away.
[*] How would you expect to arrange to meet your friends?
Some kind of nav system - you can plot a course through known systems as waypoints.
[*] How would you expect to be able to find and target them?
make your way from system to system following your waypoints
[*] How would you expect to plot a course to meet them?
galaxy map improvements - navigation from star to star pathfinding. Not hard.