Given the fairly high data rates involved I think that's a bit much to ask. At the very least for 10 bit 4:2:2 BMD recommend SATA RAID 0 and their cards need a PCI-X slot, somehow me no thinks PCMCIA or USB is going to make the grade.
Also bear in mind the resulting files are about 8 times larger than DV25.
If you simply need to get video from DB or SP into a laptop look for the Sony J30 deck. They have a firewire port that gives you vanilla DV25. No quite the same as 10 bit 4:2:2 and for DVD authoring in PAL land there doesn't seem to be whole lot more quality wise ingesting the full broadcast stuff to start with, NTSC might be a different story though.
Bob.
The only reason why output via 1394 would "Lag" is either CPU horsepower and / or disk throughput. Probably the best way to make this less of a chore is to do the CC once you've finished everything else. That's pretty much the standard workflow on any system.
Bob.