I guess it depends on what you mean by 'live gigging', doesn't it?
Personally, if you mean playing in a live band, you are going to need to play piano parts, and sometimes piano parts AND a split for brass, strings, synths, whatever. This basically means a 76. There are few of these under 30 lbs. Perhaps the E60 would do, but personally, I feel the G70 adds SO much more that the extra weight is a necessary compromise.
If, by 'live gigging' you simply mean playing an arranger as an OMB outside your house, well, everyone is going to tell you 'Use what I use'!
I think the PA800 comes in under your weight limit, doesn't it? That is a worthy alternative to the S900, with far greater capabilities (you CAN use OS2 DNC sounds like the PA2Xpro) and better keybed and construction. And a far more 'live' sound overall than the CD-like Yamaha's (great for quiet gigs and the home, harder, IMO, to make a 'live band' sound)...
However, when weight alone dictates what you choose, and precludes many worthy entrants (T3, PA2Xpro, G70), taking a good look at how others manage the weight can pay dividends. Personally, I use dollies and leverage to make sure I NEVER actually lift the G70 in it's case in it's entirety. Place the case on a chair or raised area to get it in and out of the case, and you don't do your back anywhere NEAR the stress that pulling it out of the case on the floor....
You might also consider that, in all likelihood, you regularly lift more than 45 lbs. and don't even realize it. If you have carried a child over the age of two or three, you have carried more than 30 lbs.. If you have lifted a child four to six years old, you have lifted 45 lbs.. Half of the people on this forum get as emotional about their arranger as they do their grandkids
But somehow that doesn't extend to lifting them up! They weigh about the same!
I personally think that if weight IS the primary factor in what you choose to play, it doesn't really MATTER what you chose, You have already decided that there are more important things that how it sounds, and how it works, and whether it does the job as well as can be done. Might as well pick the cheapest, you have already ruled out the best!