The problem with the 400 Whelen's shoulder is much exaggerated, it came from improper reamer specs. With a proper chamber, there does not seem to be a headspace problem. The Brown-Whelen and the 411 Hawk (Zeglin's version) have minimal taper and the shoulder is moved forward a bit, both are considered "improved" versions of the Whelen and do offer a bit more velocity and more shoulder. While it may be possible to get 2200 fps from either the BW or Hawk versions, it will be done so only at the cost of a long barrel or high pressures. 2000 fps with a 400 grain bullet is pushing into the 60,000 psi pressure range from a 24" barrel out of the Hawk.
Another problem with using heavy bullets in the 411 diameter, is the lack of availability, there are only one or two firms that are making 400 grain hunting bullets in the 411 right now. Woodleigh is one that I know of. Barnes, Swift and a few others were but have discontinued the heavies (Swift canceled their entire line of 411 cal bullets). Barnes is making a 325 grain X right now, but I believe that is as heavy as they are going (it was designed for the demand of bullets for the 405 Winchester). North Fork is still in development stage with a 360 grain bullet, and it is designed for Zeglin's 411 Hawk and should be an outstanding bullet for everything. Hawk is still making several different bullet weights in the 411 cal, and will make just about anything requested.
I had expected with the advent of the new 400 H&H Magnum and offering of the 405 Winchester by Winchester and Ruger that more bullet makers would have started supplying bullets in this caliber, but it seems to have exactly the opposite, Barnes trimmed down their offerings in the X (they used to offer 400 grain, 350 grain, 325 and 300 grain X's in 411), Swift canceled their line. It is good to hear about North Fork's addition and I'm sure Woodleigh will continue their offering because of the British rounds based on that diameter. All these are considered premium bullets are rather expensive when compared to Winchester PowerPoints or Remington Core-Lokts.
I know you can get properly headstamped brass from Zeglin's shop (Z-hat) that are made by Quality Cartridge for the 411 Hawk, but it is cylinder brass and has to be sized down for loading. This is a big benefit of the Hawk if you plan on hunting countries where they check to make sure your ammunition matches the rifle.
I don't mean to scare you away from a 40 cal based on the 30/06 case, but there are considerations you need to be aware of.
You aren't going to get 416 Rigby ballistics from one, unless you drive the pressure out of the stratosphere, there is nothing magic about them. If you are looking for Rigby velocity, energy and pressures, get a Rigby.
The 400 H&H is very promising and specs are available for it, I'm not sure if anyone has a reamer for it yet. If you are looking for 2300-2400 fps from a bolt gun with a 24" barrel with 400 grain bullets at reasonable pressures in the 40 cal, this is the way to go. Brass can be sized from 375 H&H brass which seems to be cheaper than the Rigby brass, but you still run into the bullets being expensive.