Well, an Exarch is a lot like a Sergeant, only the leader of the squad would be able to play as them. And therefore use their equipment. But they could make it that playing as a regular member of that Aspect still contributes experience towards the Exarch, so if you got unlucky and never ended up squad leader you could still unlock stuff for it.
And vertical progression wouldn't really work for some weapons, as they all work differently. Like if a Striking Scorpions Exarch picks a power claw, they don't get a pistol, or when a Dire Avenger Exarch uses a Diresword, they no longer have an Avenger Shuriken Catapult. Another example would be Dark Reapers. The Reaper Launcher is essentially a rocket launcher, while the Shuriken Cannon is more like a high caliber anti-personal (and occasionally anti-vehicle) weapon, it doesn't get the AoE that the Reaper Launcher has.
Basically, if they wanted to, they could make a reasonably balanced leveling system, but it's all up to them.

the whole access to Exarch weapons for Eldar was to sidestep the huge problem of lore allowed weaponary for aspect classes,

while LSM/CSM/Ork classes have a wide range of weapons availible to each class the eldar classes were basically limited to 1 or 2 weapons compared to 4 or 5 different weapons for the other factions classes...

this meant that eldar classes were very limited in their battleground versatility which would force the eldar players to continually have to respawn in order to deal with any change in circumstance ... so it was decided after discussion that the best way forward was to allow exarch weaponary to be availible to the eldar classes to allow much needed variety within classes

@Stelpher This was said about Exarch weapons.
Crusader asks:

"Brent - Question regards the Eldar:

Any plans for Exarch weapons available to the standard classes? I.E. Executioner for Banshees? After all we know in Lore it's only Exarch weapon, but that means basically if there are no other weapons for an Eldar Class except standard loadouts then there is not really much variety.

Or do you guys intend slight lore-bend to allow Exarch weapons for Non-Exarch Eldar?

In case of no: Can we expect Exarchs then as Elite Class with special equipment?

EDIT: Sorry if it got answered already, but I don't want to waste my opportunity to clear that up, if it had been answered already just say so and I will look through the thread to find it ^^"​

BrentEllison (Lead Game Designer, current acting Creative Designer, and Protector) answered:

"We plan to have some capacity for using those weapons because as you say, you'd pretty much have no variety as a basic class. "

- here in Official Basic Class List.​

There will also be veterans of each basic class in progression. These so far sound like basic classes with increased load out & unique visual cosmetics perhaps even unique weapons such as the Banshee triskele (or perhaps any Elite banshee has this. or hero Autarch. who knows I just want to use a triskele damnit.). Veterans and stuff were talked about in these old threads with Game Designer MichaelChan if you're interested in checking them out (note Requisition Points (RP) is outdated. Currently unknown if it's still around and what it will do now as it's purpose was split to other things ie badges.)

• "Hey Michael! Tell Us About Progression and Economy" w/ MichaelChan (Game Designer)
• "Tons of Info On Progression and Economics" w/ MichaelChan (Game Designer)

There will also be Elite classes and Hero classes. Have to spend an in-game resource to spawn as any of these ie currently unnamed badges for Elite/Hero. I figure badges for veterans too but could end up being something else. The idea of veterans came up as a different thing to spend resources on other than Elites after all (said here), back when Requisition was used for most things. Q&A Answers Compilation Thread has stuff about them. No deeper details in how they perform at this stage in development though. The impression is better, unique & specialized compared to basic classes with Heroes also buffing their team with an aura (possibly debuffing enemies or simply being super facemelters) as well as getting the enemies attention.

I think it was also said that Dire Avengers choosing to go with a melee weapon forego their primary ranged weapon. I couldn't find where however so can disregard.

Dropping by to suggest about Dark Reaper executions. I'd say it could work just fine with simply lowering the fairly massive gun towards the victim and then unleash a short missile burst at point-blank range; there's a bright flash when all missiles hit so closely together and when it dissapears only a crater in the ground and a few pieces of armor and body are left.

Do we go invulnerable during execution - or are we exposed to other fire?

Assuming we are vulnerable:

I'd argue you could use executions to reinforce roles - a Banshee could have a quick precise throat-slash (blood spraying away from the Banshee so as not to dirty her shoes) - the fastest execution animation with the least exposure to other assailants: she gets to dice people all day, err' day - finishing someone to her is, if anything, correcting the mistake of not having already finished them with her previous strike. She's almost embarrassed the kill has taken as long as it did.

A Dark Reaper could pull out a force knife, place a firm boot on the opponents shoulderblade to push them face down into the muck, place one hand on the back of their skull, and force the blade tip slowly through the back of the opponents skull - at the atlas - a soft, unearthly laugh all the while: a slow and particularly degrading execution for being killed in close combat by a Reaper.

From a gameplay aspect though, this encourages your Banshees to be out there finishing people off with their fast / low exposure finishing moves. Matching her aspect. It discourages your Reaper to be finishing people in melee, matching the Reaper aspect.

Like Eldar should, it encourages you both to work in tandem - the Reaper picking off distant targets - and the Banshee swooping between cover to tie up charging assailants and guard the Reaper, while finishing off downed opponents.

I think making execution only if I is not afraid to be killed during this time.

I think rather get in the head of the guy on the ground, no mercy, no quarter, no prisoner

How the hell did you become a mod with that English? You know what I'd like to be a moderator because my profile pic is a mouse with massive balls do I qualify?

Iam french moderator lol

And for kill enemy, english usuless !

The staff is full my friend, want to be a volunteer thank you (if you know who to stick you, you would stay a member)

Otherwise to answer your question with a fun, if you'd just put the mouse balls, there would have been no problem