For the record, there will never be a Martial Controller. We're on PHB III and 2 settings books now, if anybody had a workable idea for one we would have seen it published by now. In fact, I'm pretty happy that there is none, because it keeps a certain kind of people in RPG forums busy with one issue I really don't care about.
When talking about a new class, two things are important:
- Represents a fantasy archetype (in a broad sense that includes everything from tolkinesque and fairy tales to steam punk and oriental settings)
- Unique mechanics
Where you place your idea on the source / role grid is a second thought. For example, an alchemist class is arcane similar to the artificer, not martial.
Can already be done with a Sorcerer. Next please.
Too similar to an Invoker, especially with the Convenant of Wrath. Note that the Avenger has a few ranged implement powers for some strange reason. It's possible that we'll see ranged Avenger builds at some point (Divine Power 2?)
Defenders are melee by definition. It's what they do. You simply can't fill the defender role on range. The reason is that defenders need to do frontline battlefield control. They must get next to their enemies to prevent them from moving up to allies and attacking them. Only if you're adjacent you can draw melee attacks from soldiers, brutes, skirmishers and lurkers.
A non-ranged defender is a controller.
Somewhat of a different story would be a defender similar to beast master ranger: You summon / control one big beastie that fulfills the defender role and takes hits, and you stand back. Such a class can be modeled after the Final Fantasy Summoner.
"Trap" or Hazard Controller: By "trap", I do not mean mechanical traps, which would likely be hard to tote around and assemble mid-combat. But instead, think of an effect like Storm Pillar (doing damage to anyone who enters the area), but upgraded.
I like that one. The easiest way to achieve this one is a set of powers for the artificer, which is secondary controller anyway.
"Environment" Controller: This controller creates sustained environmental shaping powers. Lots of walls (possibly even movable!) to prevent or funnel enemy movement. Or creating pits/higher ground/other effects that shape the actual encounter area, forcing adaption on the part of the party and enemy. This could easily benefit from an Abjuration build, where zones grant benefits for allies (like concealment; again, see the Goblin Hexer's Vexing Cloud).
Druid and Wizard already do this.
Mounted Class: Mounted characters are a classic, classic trope. And yes, that does mean that they are limited to an extent, needing to take their mount with them.
I'd like to address that point elsewhere, but I do think that a mounted character is a clear archetype that could be handled.
The only way to handle a mounted class is similar to the Druid, a class with two modes mounted / unmounted.
In any case this is not a new class, but rather a new build for fighter / paladin / ranger / barbarian / whatever class you want. You simply add a number of powers that have special effects when you're mounted.
The important part is that all powers and class features must be still valid when not mounted.