Would the capacity loss (85 per cent ?) have been this huge with an ATC system based on paper strips (not as much automated) ?
It having been a track server problem, the availability of strips would probably have been of little help. The nature of the route structure makes conflict detection using a paper based system almost impossibly complicated.
If you wanted to regress to the steam age it would be necessary to revert to an airpace route structure that last existed back in the 1980s (when it was decided that they were irrelevant to the system and structure as it developed) By the time this had been promologated and all the flight plans refiled the system would have long been up and running again (IMHO by the way; I've been out of the loop for some years now)