I'm a big fan of the bauble compatible tool storage system of Tool Belt and would love to see it included as I feel it fits in very well with the fun and efficient factory tinkering this pack promotes. It gives you 2-9 slots that can be accessed by a hotkey and it is a snappy radial menu rather than hunting and pecking around in satchels.
It's great for when you want a couple hammers/picks/shovels and to hold your scanner in your first mining trips, but it really starts to shine when you are using it to store all your configuration tools (multitude of wrenches, screwdriver, soft hammer, crowbar etc).
As an aside I suggest using B:releaseToSwap=true to remove a bit of the tedium of actually having to click the item you're mousing over and instead only having to hold and release the swap key when your cursor is over the item you want. I also use B:displayEmptySlots=true so that your radial menu isn't constantly shifting in size when you have the belt upgraded to max slots. But of course this is all personal preference and others may feel differently.
Thanks for taking the time to read my pitch, hopefully this addition would be in line for the design ethos of the project, and if not then I totally understand!