I have done it once, converting a boxlock non ejector to ejector, and once was enough.

The problem is using the cocking lever as is, with no alterations, to activate the ejector mechanism. Then there are the issues of recocking on closing, timing so that the ejectors fire at the right moment in the opening arc, and timing so that they fire at the same time if both barrels are fired. The Baker style ejector is easier to do than the Southgate, in my opinion. The Baker is cocked on closing the gun by the breech face (Boss SXS use this system), it contains its own camming surfaces that automatically push the ejectors into the cocked position. The Baker can also be made more or less powerful by using different coil springs.

Also worth looking into is the coil sprung ejectors used on the Beretta 626. Not as powerful as the Southgate, but is easier to recock on closing the gun. It too uses the over center principls of the Anson but with coil springs rather than V. And finally there is the strain that recocking the ejectors places on the forend. It is a sizeable strain that might tax the engagement of the forend on the barrel loop.

It is worth considering the original purpose of ejectors: to make shooting, not hunting, faster with a loader. Not many o fus shoot with loaders and multiple guns.