And I'm with you 100%. The point that I make on the thread SNS3Guppy cites is that it's that blue line speed that marks the threshold between an instant reaction of chopping the power and the possibility of taking the aircraft into the air. Vmca is not the threshold, nor is Vr.
Blueline, or Vyse, is a little over the top or overly simplistic for a rejection decision in a light twin. We're talking about a light twin (that is, a light Part 23 twin here...specifically from the other thread a Cessna 340). Waiting to rotate or make the decision with regard to going to flying until achieving Vyse is ridiculous, and additionally puts you at considerable risk in the event of a high speed rejected takeoff.
You've asked several times here, and the other thread, what the difference is between losing your engine on the ground and in flight, and do not seem to differentiate between the two. There exists a period during the flight when one is better losing it on the ground, and there exists the majority of a flight when one is better losing it, and handling it, in flight.
Among the issues with waiting on the ground until the "blueline" for the engine failure are a lack of published data for your decision. What manufacturer suggests or provides performance data for remaining on the ground until that point? None. Each provides a rotation speed along with the relevant data, and each counts on you accelerating to the blue line reference once airborne. Additionally, attempting to come to a rest on the remaining runway from that speed with no reverse, inadequate brakes, high energy, admittadly poor high speed ground control or steering, etc is not in your favor.
If you happen to be in a light twin that isn't capable of sustained flight on one engine, as some are, then you are correct in surmising that you will be ending the flight in the near future. That's just something you have to account for before you ever leave the ground, to include forced landing sites, clearways, obstacle clearance, etc...before you ever start and engine. You're in the same boat as a single engine airplane with respect to the fact that you'll be landing...but not at all with respect to the way you do it.
You do NOT want to do the takeoff below Vmc, nor do you want to wait until Vyse to get off the ground. If you are in the air and lose an engine while below Vyse, that's not automatically cause to shut down the show,either. Part of your multi engine training in a light twin, if you had any, should have been accelerating to blue line or Vyse as you clean up. The major difference in the way this is done with a light twin vs. a Part 25 airplane is that you can't wait for 400' or any other "safe altitude" because you may not climb if you don't get it cleaned up.
What about Vxse? That speed as best angle, will be less than best rate...if you're above Vxse and not yet to Vyse, are you still going to use Vyse as your refusal point...in the air? You're above a flying target speed, but will still use "blueline" as your point to shut down the good engine? That makes no sense.
The point is that it's far too simplistic to suggest that simply because the airplane may not climb out on two engines, there's no difference in when one takes off or elects to reject, and it's far too simplistic to suggest that one wait until "blue line" speed to consider rejecting the takeoff. Moreover, it's a rather ridiculous assumption to put your decision speed at some point well after the takeoff.
Use your published data. It will provide a rotation speed. That's where you rotate. You're best rotating at that point, climbing, cleaning up, accelerating to your intended climb speed, and going flying. If you have a problem at some point in that evolution, then handle it according to the manufacturer's procedures (fly the airplane, clean up, go fly). If directional control becomes a problem and you run out of aerodynamic control and have no means of increasing airspeed, then retarding power on the good engine is your only choice. In many cases, you need not retard it very far; a slight reduction may be acceptable as you seek a higher speed, lowering the nose and accelerating, before restoring the power. It really is possible on some light twins to lose the engine, accelerate to Vxse or Vyse and climb while you bank into the good engine, clean up, and return to land.