Well, I might be a little late to the party...
First of all, having at-will powers in the game removes the need to be decent at basic attacks. How do you become decent at a basic attack? You pump your dexterity and or strength at character creation. Strength allows for basic melee and heavy thrown weapon attacks and dexterity allows for basic ranged and light thrown weapon attacks.
The issue here is that 4e isn't particularly focused on ensuring that everyone is reasonable good at using a weapon. In fact, those that are typically utilize the Martial power source. The expectation seems to be that if you are Divine, Arcane, Primal, etc... using a weapon is often, though not always, secondary.
That may not be stylistically you're thing. However, it's not that dissimilar to earlier editions. The poor 1st edition magic user's hit table was pretty bad, and could hardly be called decent with a basic attack. I think it was only with 3e (or maybe 2e Player's Options series) which brought some of these characters up to the sub-par level.
You would have 2 additional encounter powers. Encounter powers are much more powerful and would quickly knock out a lot more creatures. A controller for instance would actually be pretty good under this system imo. They could hit multiple creatures with spells that actually do more than scratch them. So despite the wizards INT based limitation they are actually contributing more with three encounter powers than they would with a myriad of crap at-wills. This could revitalize the controller role.
Would the new encounter powers be upgraded in effect as well? If not, then a wizard with 1 encounter power and magic missile/scorching burst would outperform a wizard with 1 encounter power and only two uses of magic missile/scorching burst and the rest basic attacks. Significantly.
Another important factor is, in 4e a character’s vanilla attacks are their at-will attacks. Having a special attack at will is not very special. They are not very interesting after doing them ten times every combat. It is like a one trick pony that is given a bunch of tools that can only be used in two ways. It removes imagination because when you have a cool thing like reaping strike of eldritch blast why would you ever pull out a bow throw a dagger or do anything of the sort?
IMO, they are special because they are iconic of the role the character plays. At wills help the character consistently perform his/her role. Leader never lose the ability to aid their team members, controllers never lose the ability to manage minions or change the battlefield, if even on a minor level. Taking at-wills away reduce the significance on role in the game. Again, for some people that might be a good thing.
Also, I have a hard time really understanding your "repetitive" argument. In the end, you're proposing reducing two (or three) at-wills to one (the basic attack) and I don't see how that will get
less repetitive. Instead of a two trick pony, it is a one trick pony. Certainly, increasing the number of encounter abilities can fix the tedium of combat, but that solution can be done without removing at-wills. That, and relying on basic attacks would increase the grind feel. At wills have a little something extra to make a combat interesting. Using tide of iron to push an enemy into a flanking position with rogue is a lot more fun, and makes for a shorter combat, then "I swing my sword."
Removing at-will powers opens up design space for character types that are currently sub-par by the RAW. It doesn't matter if you are martial, arcane, divine, primal, elemental, shadow, ki or whatever other power sources they are going to come up with. Characters are limited by the at-wills that they are tied to at character creation.
This makes having characters that do not fit the mold of those prefab at-wills outside the ability for the RAW to deal with and a limitation of the game system.
The perfect example is the elf cleric archer of correlon. This character is not a very viable build. I mean, what would a cleric be doing with a bow let alone a high dex. A ranged cleric is a lazer cleric pure and simple and that only requires uni-pumped wisdom to be effective. With making basic attacks the standard instead of lazers it says, "Ok I can make an archer cleric because I am not losing anything for doing it." Thus it opens up many more character concepts that were previously unavailable.
Your discussion has been focused on opening up options by encouraging/focus more dependence on weapons. The design space I see opened up is making up the cleric archer, or the cleric crossbowman, or the wizard quarterstaff wielder. True, certain at-wills (primarily those from power sources other than martial) don't really help the character swing a sword or shoot a bow. The reason, I believe, is that the expectations is if you want your character to do cool stuff with weapons, you'll look into the martial power source.
It's important to look at the role you want to have. Do you want your cleric archer to primarily assist the rest of the team? Cleric is the way to go, with maybe a multiclass into Ranger. It sounds as if you more want a hotshot archer who's also a devoted follower of Corellon. That's mostly striker, you can do that completely as a Ranger. However, if you want to add some healing and/or holy smiting, multiclass into Cleric. I think that's a completely viable build.
If, however, you simply want the characters to really focus on using weapons and don't like all that other flashy stuff, go with an all Martial campaign. Throw in some extra encounters if you think the combats are getting too dull. If you want, you can try removing at-wills in your campaign (no-one's stopping you). However, my opinion would be that it would:
1) Make combats longer unless the adversaries were scaled down. Even the current encounter powers aren't finishers, they are just slightly scaled up at-will powers (depending on level).
2) Make combat more dull as the players use their abilities early (to bring the opponents down) and then grind away with basic attacks.
3) Make non martial characters less optimized (having to spread abilities out) while allowing martial characters to optimize as they please. This would tend to make the non martial characters more fragile and probably less interesting to play.
According to your posts, I think you're trying to get away from 1) and especially 2). My opinion is removing at-wills would have the opposite effect of what you hope.
But give it a shot and see if you want.
I'm not for taking away all the benefits of a high traditional primary stat for a character, by the way - I like that aspect of 4e, too. I just wonder whether providing a scaling damage bonus would be enough of an advantage to having a high traditional primary stat, while giving the player the leeway to have a character that runs against type without feeling too disadvantatged mechanically.
