It would be nice to have RouterOS with native multi-wan support, where we could be able to add our wan links, specify link speeds and it justs works. No more hard working on PCC and/or other ways of doing multi-wan
Why even specify link speed - that can vary at times.
Multi link transmits with proper handling of sequencing and fragmentation and bandwidth are a problm that windows remote access had solved 10 years ago - PPTP Muilti Link does exactly that.
All Mikrotik has to do is implement a PPTP Server capable of MultiLink. THen you can set this up as VPN and use the nice Multi-Link functionality that will distribute traffic over the links AND make sure it remains in sequence. Something missing from other VPN protocols.
Also a request MIkrotik is ignoring - like some others - pretty much as long as I know Mikrotik.
the topic sounds like possible advanced QuickSet feature
anyway, I still can’t imagine how to properly balance links with unknown bandwidth 
Why? Other - even low feature end user routers - manage QOS without (!) knowing the bandwdith.
It is quite simple - all you need to know is to implement proper priority based queues.
queueing has nothing to do with balancing. you need balance, not QoS, don’t you?
It actually has. In a load balancing scenario you will still queue outgoing packets in a (small) queue and then have every outgoing link send packets from there - actually send fragments, so that a LARGE packet goes over the different links at the same time.
Without a small queue you can not make sure the links are properly utilized most of the time.
it’s bonding, or MLPPP - but not balancing. if you established a connection via one uplink, you cannot switch it dynamically to another uplink
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method 2 about “many more features” is waaay too mysterious
There is no method which “just works”. Something will still need to be configured, either PCC or Bonding or something else. What we could make, is an easy interface via Quickset. In this case, the configuration would be applied “in background” so you don’t have to see it.
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I would be happy if you just add an option that incoming connection goes out via the same interface it came in, regardless of other routing settings.