In my opinion, doing it in the way you suggested (mounting, doing workarounds for updating and configuring, etc.) presents more challenges than actual solutions. Sure, it may be fun to do it your way if you're interested, but the best and easiest way may be the one you're avoiding.
I recommend you get a Pi and do what you have to do on it, then make an image of its SD card. Then, use that image on your other Pis since that image is already configured.
Note: I'll assume you'll use Raspbian. I'll also assume you're just an average person and not some person who prepares images on a frequent basis (e.g. Raspberry Pi Foundation).
Steps if you do tinker with your Pi:
- Download and install fresh OS image of your choice
- Plug in Ethernet cable/connect to WiFi
- Possibly do a LAN scan if you don't know your Pi's IP addres
- Do stuff via SSH
apt-get update -y && apt-get upgrade to update packages
- Your personal configuration needs
- Make an image, then use that image for other Pis.
Steps if you don't tinker with your Pi (see note above):
- Download fresh OS image
- Mount image using instructions from https://raspberrypi.stackexchange.com/a/13138/24224 (you also have to consider what OS/image you have since some have different FS layouts)
- Find the
deb file for each and every package you want to update, plus their dependencies, plus those dependencies' dependencies, plus those dependencies' dependencies' dependencies.
apt-offline is a hassle. Refer to this link
- Then find a way to install all of those packages without using/tinkering with your Pi.
apt-get won't work offline.
deb file details here. Good luck.
- Update the Pi kernels and low-level stuff using Hexxeh's tool
- Configure to your requirements
- Write modified image to your Pis' SD cards.
I don't see any benefit in not tinkering with your Pi.
Cut yourself some slack and tinker with your Pi. You only have to do it once.