Surely the discussion of mirrorless cameras with no video has been debunked already.
The EVF is a video screen so there is already a video stream to be captured.
Electronic shutter is used for EVF and there is no mechanical cost for this in any case.
The incremental SW cost to write this to a card is small and given that that code has already been written for R3/5/6/7 etc on Digic X processor then it is a no-brainer to include it with whatever features (or not) to offer. The market will demand it anyway.
If you are saying that you want a R3 but DLSR then the 1DXiii is available for you but even that has better AF via live view.
The costs of a feature are not really an argument when it comes to Canon. Canon is famous for its "cripple hammer". They leave away some functions that could be cheap and easy to add - sometimes even via firmware - to offer a cheaper option. That makes a lot of sense for a manufacturer. People have different budgets and different needs. The way to maximize profit is selling everybody the most expensive camera they can afford. Some people will always buy the best option with all the features and others might be willing to pay half the price for a camera with less options.
For Canon it would be very cheap to include some professional video specs like time code and a few more codes into cameras like the R3, but that would cannibalize some of the really professional video camera that cost much more. That could also work in the other direction: Taking an R3 and stripping it off a lot of features to make sure that many people would still buy the real R3 for those features, but the lower spec camera could be offered much cheaper that the higher spec one without cannibalizing it. So it is not about what a feature like video costs Canon, but what it is worth to the customer.
The main reason why I would like a mirrorless camera is IBIS. I wish there would be Canon DSLRs with IBIS. That would be the best of two worlds. I would also love to have the sensor of the R3, which still is the best performing low light sensor on the whole full frame market. I understand the physical limitations of a DSLR though. In order for a 7 or 8 stop IBIS to work, the image circle has to be much larger and therefore the mirror would also have to grow, but than it would no longer fit within the flange distance of the DSLR. So basically a new mount would have to be invented. One with a larger flange distance than the EF mount has. That would result in even worse optical formulas than the EF mount has. Exactly the opposite direction of the RF mount, which has a shorter flange distance and allows better optical formulas. So in a DLSR with EF mount a strong IBIS could only work in Live View, but than you would practically use the DSLR as a mirrorless camera, just without an EVF.
Sadly photography is all about compromises. Even cameras manufacturers admit that after using the sensor for a while, it warms up and the images noise increases. That really is one of the worst compromises. A degrading image quality just because a camera warms up while I compose my shot. I think DSLRs should still have their place for situations where they can play their advantages, Just last month I bought a new EF lens, because I still believe in that system. That lens even is made of metal. Sooner or later I will probaly carry both a DSLR and a mirrorless camera on all of my trips.