So when Neo confronts him in the mansion lobby, why does he send his goons at Neo with a flat "Kill him." and appear to be upset that they fail?
The Merovingian ordered his henchmen to attack Neo primarily as a stalling tactic to prevent Neo from protecting the Keymaker. The Merovingian had just ordered the Twins to recover the Keymaker, and the Twins would more likely succeed if they didn't have to contend with the One. Recovery of the Keymaker was so important that the loss of a bunch of henchmen was worth it to the Merovingian. The Merovingian would of course be upset at the loss of these henchmen even if he didn't expect them to win.
Sure he feels disrespected by Neo's attitude but does he really expect the One to fall to a bunch of outlaws with minor (if any) supernatural abilities?
From the Merovingian's point of view it was possible for his henchmen to win -- Neo was continually growing in power and it would be difficult for the Merovingian to determine the threshold at which Neo became too powerful for his henchmen. While the Merovingian knew Neo was powerful, he didn't know just how powerful. On the one hand, he reacted with surprise ("okay, you have some skill") when Neo blocked all of the bullets fired by the Merovingian's henchmen. On the other hand, the Merovingian also commented that Neo's "predecessors had much more respect" (perhaps indicating that the previous Ones were less powerful when the Merovingian encountered them) and was encouraged that Neo could be beaten when Neo's hand bled after blocking a sword (remarking to his henchmen that "you see, he's just a man"1).
And if they did succeed, wouldn't it ruin the cycle that he must be aware is necessary?
It's hard to say exactly what would happen if the One died before he reached the Architect and made his choice. But there are at least a couple of reasons why the Merovingian wouldn't view the completion of the cycle as necessary and/or why he would nonetheless want the One to fail:
- The One and the Matrix cycles were an innovation of the Oracle, whom the Merovingian hates. If the One fails then it's also a failure of the Oracle and her system. That failure could lead to the Oracle's downfall, which the Merovingian might be able to take advantage of.
- Even if the Matrix crashes the Merovingian would probably survive since he controls the Trainman, who in turn controls the Mobil Avenue link between the Matrix and the machine world. Again, the failure of the Oracle's system of Matrix cycles is something the Merovingian can take advantage of -- it's not like he's particularly safe as an exile that the existing system is trying to delete.
We're not exactly sure how the One is chosen, but the machines evidently have some control over it because the machines designed the One to have a profound attachment to the rest of humanity. Neo is also told by the Architect that
The function of the One is now to return to the Source, allowing a temporary dissemination of the code you carry, reinserting the prime program.
The Matrix Reloaded (transcript)
Presumably the machines insert the code carried by the One. If the machines can control which human is the One, they can simply choose another human to complete the cycle if a One dies prematurely.
1Credit goes to @Jon Clements for reminding me of the sword block and the Merovingian's reaction to it.
