I prefer story which show both sides people who has to fight each other due to circumstances beyond their control. The murkier the morality is, the better. No good guy, no bad guy, no clear cut "us vs them" splitting. The age of main character preferably veterans like 21 and above. And no need for betrayal plot, just simple military style of chess game story is good enough.
Prefer realistic mecha operations, the best one is Gasaraki. The more functional mech design is, the better something like Patlabor series. Tactics wise, a mix of Gasaraki and Gundam 08th MS Team is prefered, like the fact humaniod combat asset used for peacekeeping mission which shown brillantly in Gasaraki. Mechas also do not stand still and shoot, they actually use their best tactical advantage, the ability to sidestep while firing on the move in split second ability. Urban combat and forest also ideal combat terrain for mechs whereas there is no fucking way a mech can fight face to face and win against conventional tracked armoured assets on plain or desert. Missiles were used more sparingly, not those dramatic Macross style but actually use proper LOS ( Line Of Sight) and top attack pattern. In other words, I imagine mechs as armoured and rotorless version of gunships. Greatest enemy of mechas in my abstract will be opposition rotatry wing assets and tracked armoured fighting vehicles, not forgetting mines. Exotic weapons like EM guns or Metalstorm should be used sparingly, I am more for conventional caseless auto cannons that ranges from 12.7mm to 45 mm whereas anything above recoiless rifle is much more sensible. For example primary AT weapon for Gasaraki Gowa TA is 75mm recoiless AT rifle and all rounder is 35 mm auto cannon or chain gun. Maximum weapons per armoured bipedal asset will be 3+1, with F 15 E Strike Eagle style FAST straps. Height is primary concern, any ground based mechs must not exceed 6 -7 meters due to tactical reasons.
In zero gravity combat, mechs has to be in ideal in combined arms operations, battleships will try to support the mechs using long range weapons in extreme range like for say 4-6 million kilometers. Weapons like tactical nuclear missle is ideal for long range bombardment which has robust radius destruction capability. Mechs are designed to destroy ships in short range capabilty and other opposing forces mecha assets is deployed to counter the "hunter-killer" mecha teams. Ships has limited weapon coverage ability and mechas can exploit this to maximum use. In most cases if mechs manage to "land" on the ships, the ships will be doomed as this mechs can set explosives to the hull of the spaceships and effect a hull breach which will be fatal for the ship. Ship vs ship will be guessing shooting game, shooting in dark while guessing your enemy is one I think of now.
And has to be a political thriller something like those Tom Clancy's novels, where interests of nation state or powerfull entity is treated like chess game between opposing minds like Japan and USA "chicken" game in last parts of Gasaraki.
Oh well, just some of my wishlist for an ideal mecha story can be.
