Ok, getting serious for a moment though, Doug has a point about amphibs. However, with respect, I suggest that it would be better to paint up 2 of the most popular machines that can do double duty first and then expand, rather than trying to do a 1-fits-all. That's not as hard as it might sound. IRL, operators that work in winter (and there aren't many left inland), usually convert their summer machine that's on floats to skis for the winter. What that means is that you can do one livery (and variants if you wish) for, let's say, the 185. It can be the straight wheeled version, the bush version, whichever ONE you want (and it only has to be one of those). Now, with only a minor modification, that same livery can be fitted to the other versions quite easily. For instance, with the Carenado 185, you can do just the wheeled version. Then, by adding a single section from any one of the float liveries that are already done, you can turn that into the float version, and same for the ski version. There is only one small panel in each that has to be modified, and that's easy to do (I can help with that if you need - I've done this for the Aerosoft Beaver and the 185).
With default aircraft it's a bit trickier as they didn't put aircraft on different gear for the different seasons (sure wish they had - the default Beaver is actually extremely good!). So you are stuck, and if they have an amphib machine in that, that's what I would go with to start.
Unfortunately amphibs aren't the panacea we all hope for. They can't take rough strips because there isn't the clearance under the wheels and those wheels are the most robust I've ever seen. But, for FSX purposes, if you need an all round machine, then yeah, an amphib might be the way to go.
For default aircraft, I'd be looking at the Beaver for summer and the Maule for winter. For payware machines, then I'd be inclined to go with the 185 (because you can do one skin and make that work for all seasons) and the Aerosoft Beaver (same reasons as the 185). Those are the two most common workhorses you will find in the bush today. The Caravan is making its presence felt in the bush now and it DOES operate often as an amphib, but we don't have one in FSX (and the port-over FS9 is terrible in FSX unfortunately).
By the by - just a hint about the AS Beaver: Alias the sounds to the default Beaver. AS did a great job on the flight model, but honestly, any resemblence between their soundset and the real thing is purely coincidental. On the other hand, the default Beaver was recorded from the real thing.
Hope that helps, and oh, sorry about the 727 amphib tease - couldn't resist