Marcin, OK let's agree to disagree on this one
What's more important for me is that you have correct expectations about your request. Backup I/O Control is the existing feature of Enterprise Edition and we will not be introducing point solutions to the specific issues it already addresses into Standard Edition, as this makes no technical or business sense.
As far as a couple of points you raise above:
1. You can already do that today using post-job script functionality (just have that script sleep for the required amount of time).
2. As Vitaly already noted - unlike with VMware backup which is based on VM-level snapshots, in case of Hyper-V we have no insight into the merge process due to operating with volume-level snapshots.
However, Hyper-V 2016 will have the new backup architecture that is also based on VM-level snapshots, so its behavior will match VMware backup, where the job waits for snapshot merge to complete.