I'd be hesitant to just increase the coconut oil in the summer - it still melts at a fairly low temperature. Adding additional beeswax, and subbing some of the olive oil for some Shea butter will give you a more shelf stable product - but there are limits - I keep mine in the fridge in the summer.
There are lots of Essential oils you can add to lotions to repel bugs. Catnip is great, as is citronella, clove, lemon grass, rosemary, eucalyptus, lavender.