I’ve been playing TF2 for quite a while, and my main class is medic, so of course the most obvious choice for me is the Osprey, and I’m in love with this AirMech. It is an excellent healer in air and on ground, and can do extremely well at unit management and keeping units alive, which is critical. Each unit is an investment, especially units like the Goliath, and if you don’t care if they die, you become vulnerable to a counter attack from an opponent that keeps his units alive. But how do you keep your units alive? Healing!
You need to start with your loadout. Your pilot is critical, and Kira is almost definitely the best choice, because that unit repair bonus applies to your healing. Next, the tougher units are the best ones to heal. Really any Osprey should be using Longhorns/Geminis and Goliaths almost exclusively, because they can soak up a lot of damage, and with the upgraded carry ability you can airlift 2 or even 3 of the Longhorn/Gemini tanks, which can break a position very effectively given time. Finally, use Repair Guardians to improve your survivability.
Next is actual gameplay. Be aggressive early and get that first level ASAP, you need to unlock healing quick or else you’re just a slow Airmech with a crappy gun. Once you have healing, start working on Outposts or what have you, and on your next level get the Carry skill, this allows double airlifts with Tanks. Move back and forth between healing, carry, and Guardians. Creeps are nothing compared to the Tanks you’ll be using, and you already have strong armor, so your goal should be to get to lvl 3 healing and carry and 3 guardians as soon as possible, after that everything else is gravy.
On offense, keep your units between you and the fighting, but keep the frontmost units in range of your heal beams, since they’ll be taking the most fire. Don’t bother with the capture building command, rather airlift your tanks to a clustered position in front of the Outpost you’re attacking to allow yourself to heal everything that’s taking damage, but beware bombs! If there is no anti-air or enemy Airmechs around, try staying in Air mode to keep yourself from being exposed to enemy fire. Watch your energy, and don’t hesitate to make a run to a friendly base to refill and grab more tanks, but make it as quick as possible. If an enemy Airmech is near, force him to fire on your tanks, not you! Try staying in the opposite mode (if enemy is air, go ground, and vice versa), this can frustrate and annoy enemies making them pay less attention to the tanks tearing him up when he lands. If that doesn’t work, stay in Ground mode and maneuver yourself to keep your tanks between the enemy and yourself.
On defense, try hovering over the Outpost/base your defending and healing in Air mode. Keep units clustered next to the base, and your Air heals can target them while you’re being healed by the base. Once the enemy’s attack is exhausted, do not hesitate to counter attack, since you should have a big numbers advantage. Use moneymakers on the plugs and turrets on normal ground, you can heal them yourself and leverage your economic advantage. Don’t overdefend bases that aren’t near the frontlines, since you have the best defense to a backdoor drop in the game.
Play it slow. Force your enemy to continually retreat until he is all the way at his base. Backdoor drops are great and everything, but be careful not to overextend, and DO NOT DIE. You enemy has a huge advantage if you’re dead, and you can always come back to any attack with reinforcements and your healing. If you do a backdoor drop, make it big or do two loads, and establish a “beachhead”, a safe area for you to stand and heal. Your enemy will have a hard time taking out the drop if you are healing them, and you can take out his defenses for a final push. Dropping a Goliath and getting another to drop next to it is highly recommended, the first can survive long enough for you to grab a second, and more targets for the enemy to attack means an easier time keeping your tanks alive. Heal your friends! You have to be in Ground mode to heal a friendly Mech, but a Warthog with a healing Osprey can be devastating. Also, watch for smoke on your friendly units. Grey means they’re under half health, and black means they’re gonna die soon, so keep your eyes peeled for those signs.
To summarize, use Kira as your pilot, use Repair guardians, and don’t upgrade Armor or Creeps. Don’t be afraid to take on superior numbers, you can outheal nearly anything in the game. Stay alive and use your brain, you are a Macro Airmech, not a Micro. Don’t fight enemy Airmechs, and expose yourself to as little damage as possible, and hover over your Outpost while healing your units to make it exceptionally hard to break your defenses. Keep your units close, and your enemies far away. Get an economic advantage and hold it, and look for opportunities to counter attack after a large battle.