You can export the raw displacement by configuring your export options/channels in Edit->Options->Channels and add a channel with height ground. You have several options here, with or without the water, and also in 8bits, 16 bits and, since the last update, in 8+8 bits (8bits in red, 8bits in green) or 5+5+5 bits (5 bits in each channels). Be sure to uncheck sRGB for that channel, as sRGB is used only for colors, not other data.
The height ground is exactly what I use for the displacement and for the normal generation, so I don't see why you have to blend with the albedo, it's a bit weird ...
In the Unreal engine for instance, you can tesselate and use it as displacement and it's working just fine. It's also possible in unity, but you have to do your own shader.
You can check the Export to unity or export to unreal tutorials on my youtube channel for further details : https://www.youtube.com/channel/UCMxbXJ ... 47W7auEAew
I hope this helps,