The idea of some kind of wheeled cart is (imo) an extremely good idea if a person has more than just a couple of hives. It could consist of a box containing spare feeders and jar lids (if you use inverted jars as I do), a couple of plastic milk jugs with syrup, somewhere to hold the smoker (and some extra fuel), your hive tools - and of course have some kind of frame holder - perhaps with a tray directly underneath it ? Maybe also a box holding a few spare frames ? And somewhere to hold scraps of wax. And a notebook and pen. This list could get quite long ...
Although I don't have an inspection buggy myself - I
do keep planning to make one - if only to keep all the bits I use in one predictable place. I find nothing's worse than opening-up a hive, only to find I've left something useful - like drawing pins (thumb tacks) to mark a frame with q/cells or something else which requires attention - inside the house.
LJ