|Position||+1 Speed||-1 Speed|
|Shield||+1 Armour||-1 Armour|
|Target||x2 markers||-1 markers|
|Blast||+1 Power||-1 Power|
|Terrain||-1 Size||+1 Size|
Usually the first problem with making something like this symmetrical is that bonuses and penalties, in competitive games, multiple out their effect; essentially if you give Player A a +1 bonus, then you're effectively giving Player B a -1 bonus. Although Player A just has one bonus, ignoring the face value for a moment, then they have two bonuses where one is a penalty to the opposing player. That's zero-sum for you, I suppose. However, the problem is that in choosing to do so, This is exacerbated by not accounting for the double-bonus.
So how would these markers work? They would 'stack' with other markers, but I think they should be assigned to squares, and take effect when a player attempts to do something. So a Position marker attempting to leave a square also occupied by an enemy Skill marker could affect the Speed of the Position marker. Likewise a square in which a Target marker is replaced by a Blast marker would see that Blast Marker resolved with -1 Power for that turn, and the following turn, since Blast marker have a 'half-life' of two turns, the turn on which they replace a Target marker and the following turn. A Position marker attempting to move into a square containing terrain and a Skill marker may find itself dealing with the Size penalty of moving into a larger-than-expected piece of terrain, or a square with a Terrain marker with a +1 penalty. This means I'll need to define when these markers come into player, and when they are removed.
Things like Blast markers, for example, will need to combine with Skill markers that are already on the board, and which weren't used on Target markers in the same square. Position makers, I think, would need to start their turn in the same square as Skill markers to be affected by the Speed penalty. I think, as a broad rule of thumb, Skill markers in the same square as another marker must have their bonus spent, and be removed from the board, when it is relevant.
A player with one friendly Skill marker in the same square as the Position marker for their Titan, as well as two Shield markers and two Light Damage markers could therefore decide to spend that skill marker for a Speed bonus if activating Propulsion, an Armour bonus to its two Shields for that turn and the following turn, or to Repair (discard) one Light Damage marker. The player can hold off the Skill marker, but right now I'm leaning towards the notion of Skill markers not travelling beyond the square they are placed upon activation of the Crew, and applying a similar notion to Shield markers, so that players are required to actively deploy these where they might be needed rather than tanking up every few turns.