I'm also a fan of Environmental Interactions. For instance, Wind and dist clouds. Reduce visibility, slow vehicles, possibly prevent flight. Setup some sort of Dust generator up wind from an enemy base. Or an area you don't want enemies to fly through.

A catapult that flings trees perhaps, or A Ditch digger that can block off areas by water. Perhaps even tunnelling. or hiding ships in a cloud.

Perhaps a look at Age of Mythology would be interesting to you. As far as I remember there are many Wonders that work alot like you described.

Not really by working with the environment but the effects where the same.

And Stronghold had Catapults that flinged cadavers of cows, which could cause a pleague spreading or something like it.

There is also the possibility to use some kind of zones to make gameplay more interesting. E.g. Warcraft 3 -> blight , Starcraft -> creep both as zone to build/prevent building and healing. Or the poisionous tiberium fields in Command and Conquer. But most of the time fights are far to fast over to really make them count.

Other things are also possible, like the lava that is periodically flooding the level in the Starcraft 2 campaing (or was it Dawn of War?) or the solar erruption in FTL both damaging or destroying enemies as well as player units.

And of course there is the classic, height. Units that fire from a cliff would get a bonus agains the units down below.

If you're looking for a departure from the classic RTS you should look at Majesty 2, where the player isn't controling units directly. You are only setting bounties for specific tasks and the heroes/units will do them if they decided it's worth it. From the earned bounty heroes could buy weapons, armor and potions.

Each unit also had a level like in RPG's (not those silver/gold or veteran/elite labels) and you could put them into parties to increase their chance of survival.

Somebody may disagree with me on this but Starcraft (or Starcraft 2 which is practically the same) has everything one would want from RTS game. That is base building, multiple races, multiple resources, near perfect balance inbetween. But for me in all RTS game after a while it boils down to -> do this, this and this in exactly this order, under certain amount of time and you will win.

I completely disagree. I feel Relic has a far superior system seen in Company of Heroes and the Dawn of Wars. I will touch on what I love about them below and what I feel is necessary as well. Don't get me wrong SC2 has a tremendous following, but that doesn't mean it's the best RTS available.

I love Dawn of War and Company of Heroes over say Starcraft for two reasons. Simpler micro managing and no gatherers. The gathering is based off of territorial control which in turn forces combat. Simple micro managing lowers the skill base while still allowing room for expertise. By forcing combat and lowering the skill level required to compete you have now turned a time-sink RTS into a Thinking RTS, which is where I think most RTS' lack.

Other things like cover are just icing on the cake.

With that said here are some things I think are necessary for RTS:

• Two (or more) Resource System
• Objectives to force combat/taking actions
• An easy to understand Rock-Paper-Scissors unit approach (Doesn't have to be direct counters, For example AA guns hurt tanks in Company of Heroes but they do extra damage in the rear, Self Explanatory really but it makes you want to get behind them, but you don't have to and can still be effective)
• Keep the "racing to perform actions" to a minimum and the choice of "what actions do I take" at the forefront

Like another poster said I too also enjoy a limited number of unit choices but I don't mind if I have a small army (Company of Heroes) or a giant one (Homeworld). I

I like when not only are there different races, but when the races play completely different. For example, in warcraft 3, one race raises the dead and for another race almost every single building can uproot and attack the enemy or otherwise has a purpose like healing units. There should be completely different gameplay if you decide to have multiple races. Playing a different race should mean an entirely new experience. Otherwise, I wouldn't recommend having different races.

I despise micromanaging things. Micromanaging is what keeps me from getting into these games besides playing a bit of the campaign. It sucks when you have to tell all your units to target one unit (not to mention it's unrealistic). It's one of the reasons I like to play MOBAs, as there's plenty of strategy without having to command every single unit on the map.

Custom unit specialization

-Everyone starts as a basic soldier, I get to issue skills, gear and weapons (a la FPS) these custom units could be preset at structures and units could be assigned to report to those structures for upgrades.

Veteran command units.

-Surviving units that earn skills to become caster units or can have X # of units linked to them enabling that unit to tactically organize of those units.

Veteran training

-Assign a veteran command unit to a structure and custom specialized units can be trained by the veteran unit to be deadlier soldiers. Example: A veteran unit earns the ability to use (cast) grenades. The player applies the unit to a structure all units trained at that structure will tactically use grenades when they are equipped with them.