The popular German enterprise IT magazine iX did a big article about WAN optimization in their last issue (2/2016). Part of the article was testing Open Source solutions. The clear winner is SoloWAN (https://github.com/centeropenmiddleware/solowan). They did tests for cifs, nfs, https and http traffic and everything except HTTPS got a real big boost. SoloWAN is Linux userspace only and gets the traffic via iptables nfqueue. This would be a real cool feature for RouterOS and should be fairly ease to implement - please implement it!
not so much “non-userspace” in ROS.
cuz linux kernel and netfilter was only perhaps common thing between generic linux distros and ROS.
With userspace I meant that there is no kernel patching needed as the mikrotik kernel is heavily modified so that would be tricky to apply. A user space program with only a few dependencies should be much easier to integrate. 
you can use “meta-router” or “OpenFlow” features on relevant platforms(MIPSBE and PPC), probably later for that, i guess.
and again, there isn’t much “user-space” in ROS, sadly.
thats why for example MikroTik - failed to DIRECTLY adopt Native “Zero Overhead Linux” from Tilera for CCR routers under new disguise/shape, for example, despite TREMENDOUS beenfits(not only on this platform)on such application and outside it.
ppl do make various “aplliances” for “meta-router” and use them on “powerful-enough” routers(starting from 450g and 850gx2 and things like rb1200). but using “openflow” in enteriely new thing/beast and open potentially new horizons for platform itself.
generally SDN - was one of reasons for Linux adoption by Microsoft for example 