Everyone uses lipo packs underneath the board from what I've seen.
I think battery packs with a wire to your pack would be kind of dangerous since there are times I jump off or want to get off without anything attached to myself.
I do swap packs occasionally but it's much less since switching to 12S 5ah.
Here are packs in sets which I velcro together and have velcro on the bottom which are secure on the board. I then wrap them in these 7"/8"/9" soft tablet cases. Fits perfectly. Wires are wrapped around the sides and separate from each other to prevent any shorted connection within my backpack.
I usually grab 1 or 3 packs depending on the Wh/Power I need. I also added those green/red battery slider things on hobbyking to know if a pack is full charge and/or no charge.