Convert!
I did something similar to what you are proposing to do. I had a really nice Jeep, and had planned to keep it as long as possible (Since they have yet to discover a cure for automotive ADHD), but was pulling my Chaser up the Million-Dollar Highway into Ouray in September and got passed by a Canadian tour bus! I thought to my self, "Self, this is stupid!". I mean, I put thousands upon thousands of dollars into my Jeep and it was incapable of pulling a sub-1,500 lb trailer up a mountain?! That is unforgiveable. I went shopping for something a bit more powerful and ended up with a Tacoma. I haven't looked back since. The good news is that my wife is looking to replace her Grand Cherokee soon and I have her halfway convinced to get a TE 4Runner. I think that you would be doing yourself a favor if you went with a 4Runner for an expo platform, especially given the availability of aftermarket support, the way the trucks hold their value, and the proven reliability. Just don't make the mistakes that I have made over the years with vehicles - buying one and spending thousands of dollars immediately after the purchase on aftermarket. It's amazing what a stock platform is capable of and the more mods I do the more inherent flaws are revealed in the vehicle. Modify intelligently.