As you have wireless, two options exist how to bridge transparently over wireless network,
WDS and EoIP.
EoIP might create additional overhead, you can try with WDS.
today i am just finish to make link with wds and bridge [ap2ap] one site use RB511+omni 15dbi and other side RB511+19dbi flat antena around 7,6km, signal: -77 - -79 noise-floor: -102 los ofcourse. freq: 2,4ghz
again, before i am not belive about link, Thanks Mikrotik and Team