For what it's worth, these are my thoughts (copied out of an earlier thread on a very similar question with a few edits):
I agree with not skipping the meseta (Burgos to Leon)--that was very meditative walking for me. I would, however, skip the cities. The concrete and asphalt of the cities killed my feet, and I did not find the urban areas that spiritually or visually nourishing. The cathedrals are architectural wonders (although touristy), so you might bus in, see them, then bus out. Some people do not like this approach as it seems their spiritual lesson is to keep walking, even through areas that are not pretty or uplifting. My spiritual lesson is that suffering is optional. Everyone is at their own place. I think you'll figure out what you need to do for yourself as you walk.
If you do decide to skip the urban areas, often you can just use the metro buses--take them from the first place they appear into the city center, then back out again (we did that out of Leon and should have done it into Pamplona (except the bus was completely filled with San Fermin celebrants).
Specifically, I would do this around Pamplona, Burgos, Leon, and definitely Ponferrada (which I found to be a gang-tag filled urban mess). Logrono is a nice walk, both in and out. For Ponferrada catch the bus or taxi in Molinaseca--the walk from there is all concrete and asphalt. We then took a taxi to just the next hamlet outside the city, and started walking again. For Leon we took the bus from Mules and then the metro bus to Virgin del Camino.
Finally, there is a nasty bit of road walking after Villafranca Bierzo (spelling of all city names is approximate) just as you are re-entering the mountains. From there, I highly recommend the "high route," which was steep but the nicest day of walking we had (take extra water). If you do not do that (and no other pilgrim did it the day we walked), you will be walking by a busy highway separated by a concrete barrier. That is bad enough (and I would take the high route or a taxi--I would not walk the low route), but then, just after Trabelo, the barrier ends, and you are walking with rather large trucks whizzing by within a couple of meters of you with no protection. I consider walking that section to be the most foolish, dangerous thing I have done in years. If (when) I walk it again, I would definitely take a taxi through this section. Start walking again at Las Herrerias, where the Camino turns on to a much smaller road.
If you take buses/taxis around those 4 cities and the section after Villafranca (and if you need to make up time, the whole section from Molinaseca to Las Herrerias), I think you will have time to start in SJPP or Pamplona and walk the meseta and everything else except the urban areas. Should I ever be fortunate enough to have time to walk the Frances again, that is how I would do it, even if not pressed for time (I could always use the extra time to go to Finisterre and Muxia).
I hear and understand the concern about leaving behind your Camino family. This is a real concern--they become your support network while you are doing the most physically demanding thing you have probably ever done. My experience doing what I have described is that these little jumps around urban areas did not result in losing them. Perhaps it was because my badly mangled feet (another thread) limited my kms/day, but I found that we kept connecting and reconnecting with our family. YMMV, but its worth thinking about starting in SJPP or Pamplona and skipping smaller sections rather than skipping one huge section in the middle (which would surely result in having to reestablish another Camino family).
Buen Camino,
Jo Jo