You're going on a cross country trip aren't you?
if you're concerned about roos/camels/cattle/etc then certainly do all the items suggested above, but do be aware that unless you do some pretty drastic modifications to the inside of the headlights you won't really be able to get the high beams broader, brighter bulbs will help you see, but the beam is limited by where the lens/reflector directs all that light.
I would suggest buying a pair of driving lamps and fitting them, they will allow you to get more light, and more the point, direct the light to where it is needed.
You would be able to mount them somewhat splayed out so as to direct more beam towards the sides than usual (so the high beams light the middle, and the auxiliary lamps light the edges)
the "mouth" of an MX5 can easily accomodate a pair of 4inch round lamps without any permanent modifications, all you need to do is to make up a bracket to hold them, and then attach that bracket to the existing captive bolts for the number plate bracket.
You can see what i'm talking about on my car here:
2nd by
hks_kansei, on Flickr
note, my number plate is off to the side purely by my preference, it would have still fit with the lamps in place.
Those were my old lamps (NB8B Cibie Fog lamps), which had a great beam pattern but were removed after one got broken. I've now got another pair on that look neater (Unbranded chinese), but have an absolutely garbage beam and are way too bright despite being labeled as fog lamps (they're as bright as my high beams)
in saying that, the foglamps broad beam shape, with the high beam brightness, seems to be exactly what you want.