I see this argument regarding Bo9S and 4e very often. But can you explain why you think Iron Heroes took the 'making everyone spell casters' approach?
Traditionally one of the big disadvantages fighter types have faced compared to spell-casters, is that however formidable the fighter was at doing damage, it faced the serious drawback of not having a tool chest of abilities with which to deal with obstacles. By contrast, the spell-casters ability to break the laws of reality allowed them to overcome whatever obstacle they faced. This is one of the most serious design challenges you face when designing a fantasy game. On the one hand, you want to offer the player of a spell-casting character the oppurtunity to fly, turn invisible, summon creatures, conjure items, manipulate things with their mind, and all the other fun stuff. But on the other hand, you don't want to have the spell caster completely outshine the player whose character concept isn't 'Wizard' or the equivalent.
One way to handle this is give fighter types a toolchest of reality bending abilities of their own. In some cases, you give a mundane explanation for the reality bending, but in general you can tell that this approach has been adopted when the mundane explanation for something becomes far less important than achieving the result.
In other words, one approach to designing fighters might be, 'Imagine all the things that Batman (theoretically a mundane individual) might still be able to do without a utility belt, and then provide the rules to allow those mundane (but superheroic actions)' In this approach, what's important is that you can rationalize the ability, and having rationalized it, in theory anyone - including a wizard - can attempt these 'feats' albiet probably without the chance of success a super fighter would have. The contrary approach is, 'Imagine all the things that a fighter needs to do to be competitive with our wizard design, and then provide them as fighter abilities even if we cannot think of a satisfactory explanation for them'
It's quite easy to tell which design approach dominated over the other in 4e, Iron Heroes, and Bo9S. As a glaring example, consider the Hunter's ability to create a ladder by quickly shooting arrows into a wall. This is an ability restricted only in that it is restricted to the Hunter. Why can't anyone reasonably accurate and quick with a bow do it? Why is it a class feature at all? Why doesn't it matter very very much how hard the wall is? Or similarly, the Hunter gains the ability to cause an opponent to trip which specifically works regardless of the terrain involved or the foe. Why does this work? Because this isn't actually a mundane ability, but a 'spell' in a slightly different form.
And what is this 'being like spell casters' for you? Having an ability to do something once/ encounter or day? Or is it something else?
It's a combination of things some of which is perception based on my play background (mostly D&D for fantasy games) and some of which is based on the above.
Being like a spellcaster means to me:
1) You have one or more abilities that specifically grants you exemption from reality. You don't have to justify the reasonableness of what you do to the DM, because it says in the ability what you can do.
2) You have limited resources, generally constrained by time. You can't use your ability however you like, and instead the game constrains you to only use it so often with your ability recovering over time. Whether this ability is constrained by mana, fatigue, spell points, tokens, or direct limits per time interval depends on the system, but they all basically force you into resource management with your abilities.
You could also design a wizard to work like a fighter class by constraining the wizard such that it has class abilities which don't do much more than damage or similar combat based effects, and then you allow the ability to be used at will. At that point, the fact that the damage is coming from bolts from a wand or arrows or thrusts from a spear is little more than setting dressing.
4e in my opinion did both. Fighter classes got alot more like spell casters. Spell casting classes got alot more like fighters.
