The medical kit is 600 credits, so it can fall under that clause. Unfortunately, the surgery kit is 1000 credits, so you have to choose which one will be "weightless". However, as I said before, you can miniaturize the surgery kit for an extra 500 credits and it will weight half (5 kg).
In the case of the Mev, use this rule to ignore the weight of the medical kit, which leaves 12kg for the armor, 10kg for the surgery kit, and 6kg for the medpacs, for a total of 28kg, which falls well within the 36kg limit of a strength score of 12.
The problem with large droids is going to be extra costs, trying to move in and out of some locations, and trying to avoid being attacked. The more legs, could be a decent alternative, though it may not be high enough -- on the other hand, it also makes you very different (and costs more).