Get a Jeep JK/JL or a mini truck that's already built. Then get a tow rig and trailer. Keep an eye out for rigs that have already been built up, alot are sold on forums. That's gonna be your best deal. Marlin has a forum with some cool rigs for sale.
The FJ is one of the best do everything, street, trail etc.... (along with a 4runner but people rarely build those for "crawling") With some mild mods the FJ can do any trail before you start talking eminent body damage. Like 8+/10 type stuff.
It always amuses me what people consider to be underpowered. I've taken my FJ on 37's, stock gears, a crap ton of armor, no sway bars and still easily drive it faster than anyone else on the road, including 85 down the highway. Yes its loud, but underpowered? Nope.
4th gen 4runners have V8's from the factory, people have SAS'd those. And you touched on the reason I have crossed out the SFA. It usually takes a few tries to get it dialed in, unless you spend $20k+ front and rear to have it done right by one of the very few shops in the country. Start counting months out of your hands, shipping etc... it all adds up.
Have you heard of the new Marlin RCLT? Cheaper than a SFA and just as strong and you can install it in your own garage. http://board.marlincrawler.com/index.php?topic=103556
He's supposed to announce the price this month, then you can make up your mind.
I'm getting a rear diamond axle, 14" Kings in the rear and RCLT. Most likely an Atlas later on. All installed in my own garage. Point is, think outside the box for yourself and challenge what other people think is possible with the FJC platform. For the trails I do it will be amazing and I will still be able to drive it across the country to get there. The whole point of owning an FJC. If I wanted to just piddle around on the ORV trails near me I would get a cheap minitruck and trailer. Then tow it with my built FJ.