This discussion may be more appropriate for the main SW thread since this is the "Unit Requests & Progress" thread.
I like the idea of having primitive ancient units in the game, but I'm not sure about giving a full era to pre-blasters, hyperspace, repulsorlifts, droids, etc... This creates a problem off cramming all of the units from the movies to the new republic into 3 eras. On the other hand, maybe we could have the 1st era be entirely an ancient era that is
shorter on techs and make the last 3 be
longer so that this cramming too many units at once isn't a problem. The good thing is that we don't need to make new graphics for most of the ancient units since Jobiwan & Odin have already found some good substitutes, except for maybe those colonial Spanish units.
Influenced by recent suggestions, here's how I envision the tech tree and unit upgrades:
ERA 1:
Early Republic/Beginning of Galactic Expansion/Great Sith War
*Fighting in this era is mostly infantry based
*Start off with primitive infantry units
*Jedi & Sith Orders are founded (1st Jedi & Sith units)
*About midway through blasters and energy weapons are discovered (Better Infantry & Light Turrets)
*Mounted units are available
*1st Droids become available (Regular Worker unit upgrades to the faster working R2 Droid unit)
*Early space transports, starfighters, and shuttles are available towards the end of the era
ERA 2:
Republic & Separatists > Episode I-II
Rebels & Empire > Episode IV-V
*Coming into the CW/GCW era
*1st Repulsorlift & Mech units are available at the start
*More efficient Hyperdrives are invented (ships can now go deeper into space)
*Commerce Guilds are formed
*Better Transports, Starfighters, & Bombers become available
*The 1st Capital Ships come at the end of the 2nd era
*Gunships also become available towards the end of the era
*Capturing & Trading for resources is now essential to building a growing arsenal of units
ERA 3:
Republic & Separatists > Episode II-III/Clone Wars
Rebels & Empire > Episode V-VI
*The peak of the CW/GCW
*The 1st Walkers appear on the battlefield
*Heavy Mechs & Fast Fighters can now be built
*Mech units are now dominant on the battlefield
ERA 4:
Republic & Separatists > Episode III-Early Empire
Rebels & Empire > Episode VI-New Republic Era
*The end of the CW/GCW
*Everyone has their best units
*Infantry is more defense oriented since mech units now do most of the invading
*Technology has advanced to the point that Command Ships & Superweapons can now be constructed
*This is where some of the EU units might come in
Also, I have some suggestions for how to make infantry practical. First, have infantry units be created every few turns at cloning facilities/droid factories/recruitment centers. Second, have them be upkeep free. What do you think?
That's a good idea having infantry being built by improvements, that way your military will have some infantry units in it. This idea may need some experimenting to see how effective it is.
My last idea

is actually one I had a while ago. I had suggested shield generators as a city defense unit. I am trying to make that unit. Here's a preview of the shield absorbing lasers (attack anim):
Bringing these guys back eh. . . I still think for the main mod shield generators should be an improvement, since nothing can keep you from building and fortifying a whole bunch of shield units in a city. However, the shield units can work in a Battle of Hoth or a Battle of Endor type of scenario where we can place just 1 shield in a city and make additional shield units unbuildable.