I've been playing a few starts on these settings and one surprising thing I've noticed is that, without fresh water, despotism is a pretty good govt. Without the ability to irrigate, very few tiles are affected by the despo penalty. Furthermore, many more tiles are going to be useless than normal. So your cities are going to be small. This means that the free unit support more than makes up for the additional commerce from Republic. A govt switch should therefore come much later than normal.
Other observations:
* If you go for the Republic slingshot (and I suppose you should even if you don't switch) you'll have no problem getting it. Depending on how bad the start is, it could come as late as 900 BC but you'll still get it.
* Locations suitable for building the GLH are hard to come by. Furthermore sparing a city for this purpose comes at a heavy cost, because you will have so few of them.
* Try not to build cities on grass. There are few enough tiles you can work without wasting them.
* The cases where you want MM early are fairly rare but they exist.
For some reason, I seem to share an island with Cleo three times out of four.

If there's another civ, it's usually Alex. Odd.