Do you know of anyone who has done such a conversion? Seems to me they'd have to hack up the center console a bit.
Biggest drawback to that, IMO, is that you'd lose the multi-mode capacity which is one of my favorite things about the 4th gen. I would actually just repair the pushbutton (as much as I hate it) before I got rid of my MM capacity.
From what I've seen over on the T4R forums, the people who have the most trouble with their pushbutton 4wd are those who rarely or never use 4wd, then they get hit but a sudden snowstorm and when they try to switch on their 4wd, it doesn't work.
So, what I did last week when we had several inches of snow in the forecast, was to make sure that the day before the storm, when the weather was still nice, I switched into 4wd with the center diff unlocked and just drove like that to work. It took about 30 seconds to finally "click in" to 4wd and I just drove it like that all day. Next morning, with snow and ice on the ground, it was still in 4wd and I drove it like that.
My experience (which is very limited, since I bought my 4th gen at the end of June) is that the "first time" you put it in 4wd on a cold day, it will take a while for the actuator to move and put the vehicle in 4wd. But once you've gotten it in and driven it that way, it switches back and forth very quickly. Like anything mechanical, it needs to be 'worked' periodically or it gets sticky.
Of course, the biggest advantage to multi mode is that you can have in 4wd/unlocked on paved roads without doing any damage. So I figure I'll just put it into 4wd whenever the weather forecast looks sketchy and leave it there. At worst it will cost me 1 mpg or so, and since it's not my DD, that's not a big deal.