I think you hit the nail on the head mike at least about the 24-70/4. Instead of introducing a new lens why not work to improve the existing ie you've got a 24-70/2.8 why not see if you can produce a 24-70/2 or around there. Not to mention IS is great for hand holding for relatively long exposures but I find once you're shooting anything fast moving or with exposure times longer than say 1 that IS does next to nothing maybe it's just me but paying for IS lenses seems like a gimmick when if you know what you're doing you don't need IS you can compensate with faster F-stop, therefore producing faster shutter speed or hey why not just invest in a tripod for the long shots that's what I do personally unless I'm in an environment where a tripod isn't practical then IS MIGHT make sense otherwise meh.
Sorry for the rant just had to get that off my chest about the IS lenses and their pricing just because of the IS.
Secondly on the 70-210 F4 being a garbage lens I'd have to disagree there Mike. I know with that said that you're comparing it against high end glass that costs a lot more money to invest in. True hand holding it at 210 at F4 is difficult to get a great blur free shot but the same could be said of any F4 lens without IS (very long zooms are where I totally get IS and it makes sense to me btw). As for some other points (ie that it's soft wide open well of course it will be most lenses are unless you pay a premium. I find most of the time I shoot it around f/8 and it produces wonderful images at that setting F4 is great for DOF though. With that said if I wanted a lot of DOF and bokeh I just use my 50 1.4 as that's what it's made for. I invested in the 70-210 F4 specifically for shots where a zoom was needed and I couldn't get the shot any other way without getting in the way of someeone else's shot (ie my best friend's wedding which I shot over the weekend in partnership with 4 other people). True the 70-210 had some trouble with the lighting if I tried hand holding it but sitting on a tripod that I could move around easily to get the angle right it produced excellent quality pictures. So I'd say that yes it's not the fastest lens on the planet (it's 25+ years old give it a break) and yes it's before USM so the focusing isn't the fastest and it sounds like a toy car HOWEVER use the lens to it's strengths and it is an excellent quality zoom lens that I would pit against just about any of the consumer level zooms today and I can tell you I'll get better quality out of it than them. With that said i just picked up a 28-105 USM II tonight and have been playing with it so it may replace the 70-210 for day to day zoom needs though I know the 70-210 will still be a great lens for airshows or what not like that where the extra range makes a huge difference.