So this may seem a little long winded and presumptuous, but bear with me.
Rotarycraft could use a complimentary mod, which makes Titans. The titans would justify the amazing and powerful defenses rotarycraft offers. Titans to build as grand projects, NPC titans to defend against, perhaps even NPC strongholds to send the Titans up against. NPC titans and NPC strongholds would have drops to build a tech tree of better titans. Of course the multiplayer possiblities are interesting too.
Preliminary thoughts:
Each player (or team) is limited to one of each class
4 classes, based around different building materials.
Metal (ranged titan)
building materials like metals and gunpowder (finally a good justification to make tons of sawdust, charcoal, gunpowder...kinda always wanted an excuse)
Flesh (Melee)
You'll need lots of animal meat, and giants swords and shields too. Tempting to allow tie in MFR's liquid meat, or blood magic's blood.
Plant (Healer)
Mostly made of wood. Tempting to tie in MFR biofuel as the blood in it's veins. supports metal and flesh titans
Clay (Buffs)
Made of types of clay and dirt and other similar materials, supports metal and flesh titans
Balancing could be tricky, as could dealing with certain tricky types of defense a player may put up, like moats, tiger pits etc, or blocking with materials that are usually unbreakable. There should probably also be an action the player takes in order to enable the potentially lucrative business of provoking titan attacks on your base......Maybe stealing an object after assaulting an NPC location, and placing it somewhere that NPC Titans will seek to recover it and smash you good.
The thought of scaffolds around a giant not yet mobile offensive juggernaut is pretty cool, pumping in various fluids and materials etc... and the thought of blasting away at the onslaught and collecting loot to advance your own titans for greater tech tree stuff is pretty appealing.
Ok.....Get busy Reika