OK, looks like Scotty is on the road or something, so I'll give it my best despite only being 70 kilos.
On the original question (replacing the E74 with something looser) already the 08 or 09 EVO 75 xtv will do that. They are exactly looser int he top turn in the sense that it is much easier to set a rail when coming into the top turn with speed.
Another alternative is the upcoming Evil Twin 74. It is overall rather similar to the EVO in feel, but the top turn particularly is looser and less locked in. Especially on steeper waves you can get away with more radical top turns.
As you say the ETs have a fair bit of EVO heritage in them but they have even more hip. This was done to make them go vertical better, but it gives them some extra area in the back too which of course helps in less than ideal conditions. I've sailed the ET 74 in slow waves and cross on - the usual wind blow stuff we get here in Sweden, and it does this really well. I've sailed the ET74 in 40 knots (cross on), and it does that rather well too - better than the EVO 74/75 I would say. So, it's a board with a really wide range for me and I think it will have a wide range for you to (but shifted towards a bit more powered up stuff since you will not float on it as well as I do).
It's rather hard to replace two boards with that much of volume difference (87 and 74) with only one board. You've inevitably gonna loose something. If you're gonna do it maybe the ET 80 is indeed the best alternative. It has reasonable volume and I think it will still be loose enough. But probably keeping the 87 (which is a nice board but still will not sell for that much anyway, I suppose) will give you more options in different conditions. Then, especially since you mention 40 knots, the ET 74 is the right way to go (unless you want to play safe and go for the EVO 75).