I've been testing via VPN from London (Kent -> London VPN -> then across to FFXI servers), and that has removed the constant R0s and disconnects for me, instead I see everyone else red dotting.

My other char I have connected this morning via Tokyo VPN but I haven't been home to test if it's been R0ing or not yet.

I've found in the past (when trying FFXI from crappy hotel Ethernet) that there is a control connection that is not constantly kept alive alongside the main char data connection, and things like Hotel firewalls close down the control connection thinking it has expired and about 1 minute after logging on POL kicks you out. When using a VPN it bundles all traffic together so this control connection can't be blocked separately. I'm wondering if something along the network hops is interfering with this control socket as sometimes I've seen my chars suddenly kicked (R0 for only a second), other times R0 gets down to 45% but the game recovers.

This still doesn't narrow down whether the issue is at FFXI server end or along the path, but certainly using a VPN is curing it for me. Not a long term solution of course.