I prefer the reroll OPG... it makes the MTB unique and doesn't create a crazy synergy with the Russian MTB that creates smoke.
Giving it two saves (Hi-Speed Evasion and a +1 on concealment I believe should increase the cost), granted only the concealment works against aircraft... but the two saves vs. Surface ships can get SUPER annoying.
This becomes a rule question then as you WOULD can an advantage of smoke in an island.
1) Typically a unit in an island has it's line of fire blocked into and out of that sector, but gains no advantages while in the sector. 2) A unit in smoke, fog, and Squalls have line of fire into and out of its sector. Additionally those units gain a concealment roll against attack both in and out of sector.
Per the rules a unit can gain benefits form different sources, in this case 1) the SA granting it concealment in an island/coastal sector and 2) Smoke or a Squall granting it concealment.
There is nothing in the rules (that I can find) that state you can only gain a concealment roll from only one source. Therefore you would get two saves in this case. (Fog, Smoke, an Squalls are not stackable as they are specifically covered in one section of the rulebook.)
Just as a reference point I'm looking at page 32 of the revised rule book under Line of Sight.