I would much rather see stacking.
MLAG is fine for Layer 2, but it's a nightmare for Layer 3. Stacking works well for both. Considering a lot of the CRS3XX chipsets have L3 HW offload that has yet to be taken advantage of, it would be nice to be able to form an LACP chanel across two or more switches and use it at L2 or L3.
If the MLAG is active-passive (like in IOS-XR), then Layer-3 is very easy, because only one of both routers has an active/running interface. The distribution needs to be done by a routing protocol, of course.
I wonder if it would be possible to fake active passive MLAG using VRRP between both routers for Master election (including a separate HA-link to prevent split-brain). Then employ a script that checks the VRRP-Status (Master or Slave) and accordingly brings up or down the local bonding interface.
Of course the chassis-id needs to be the same on both routers.
The only downside is, that mikrotik forces you to include at least two interfaces in one bond. But you can always use an EoIP-Dummy-interface to circumvent that.