You can use Mikrotik APs in 802.11 with wds-mode=dynamic, and ubnt stations with WDS enabled if you need true layer2 transparency with no inter-operatibility problems.
However, to extract the maximum from your infrastructure, you should be using a wireless mode that uses TDMA.
Each brand has its own, propietary TDMA implementations which aren’t compatible between them: Mikrotik = nstreme / Nv2, ubnt = Airmax
Mixing AP/station brands prevents you from using TDMA, forcing you to use regular 802.11 wireless protocol (no TDMA), which won’t scale as well as TDMA.
Your equipment choices aren’t ideal:
1.- You’re mixing brands (No TDMA)
2.- You’re using an Omni, which is the worst choice for regular AP deployment
3.- You’re using a dual chain AP radio, with a single chain station radios
4.- You’re using a station radio (bullet) that additionally needs an external antenna (more expense, and chances of the N connection developing problems due to weather).
I’m not sure how cheap you get the airgrids/bullets, but I doubt this setup will save you money in the mid, nor even in the short term if you factor in single chain performance or extra costs like the external antenna.
I’m afraid you picked just the worst possible options available to mix.
Use same AP/station brand equipment. You can use budget-conscious equipment, like integrated sectors as the SXT SA, and mANTBOX. Great CPE options to match: SXT lite (until 5km), LHG-5 for > 5km.
That will enable you to make the max out of the equipment, exploiting TDMA, dual chains, and the lack of external antenna connectors will save you from one of the main typical sources of problems.