Raypak heater faults and rusting out

10 years is a good run on an outdoor heater. You keep the next heater from rusting out as quickly by running it once a week or so for 15 minutes to keep moisture from forming rust. A heater run often lasts longer then an idle heater..

I will let @Pool Clown @ps0303 @swamprat69 issue the formal death certificate.

Those metal strips hanging down are part of the flame tray where the natural gas burns. I would not run that heater in that condition as you could get flame roll out to the bottom of the heater. Sort of looks like a small animal (rodent) may have gotten in there and was pulling it apart to find a place to sleep. It looks like it needs to be rebuilt but with the bottom all rusted out like that, you may just be throwing good money after bad.

Time for a new heater in my opinion ... and yes, run it more often.

A few things...
Yes, those are the flame rails or burners. They have become disconnected from the jets and the heater should not run like that.
Assuming that the heat exchanger is not leaking, the only moisture that you would get underneath the burners is condensate. Not only does the water itself promote rust, but also the Low or acidic Ph of the water accelerates the rusting process. You can get condensate when the heater is heating the water from a Cold temp to a warm or hot one. Your not going to get condensate the whole time it is heating, only as the water temp passes up through a certain temp range (as its being heated). I want to say it stops around 68 degrees. I used to remember more... The fact is, your going to get it, and you cant really avoid it UNLESS the water never drops below the low 70s. What I'm getting at here is, running the heater "every so often" to keep the rust away won't. Don't get me wrong, you should run it every so often, to keep other components from failing prematurely. Having said that, Raypak has done some improvements to the floor of the heater since 2007 with regard to rust resistance, and you will see it when you buy your new one.

I would say stay with the brand you have, Raypak. If you decide to get a larger size (BTU) you will have to assess the gas line (size) to make sure it can handle the extra gas demand or volume requirement of the new heater.