Lancelot as Feste... or Dogberry?

I thought I had Lancelot's character figured out early on in the play. He reminded me exactly of Dogberry from "Much Ado About Nothing". Like Dogberry, Lancelot would make slips of the tongue that were words that sounded similar to what he meant, but were not what he actually was intending to say. As Dogberry would say to Leonato "Marry, sir, I would have some confidence with you that decerns you nearly" (Much Ado About Nothing 3.5.2-3) when he means to have a conference with Leonato that concerns him, so Lancelot would say to Shylock "I beseech you, sir, go. My young master doth expect your reproach" (2.5.19-20) when of course he means approach. It gives Shakespeare an opportunity, however, to touch upon another matter while holding an entirely different conversation. Shylock's reply to Lancelot is "So do I his." (2.5.21). Shylock is not talking about approach, but about reproach. Lancelot believes he is holding a conversation about whether or not Shylock will come to Bassanio's for dinner, and Shylock is insinuating that Bassianio will further insult him, which in Shylock's defense it is likely that he will. Shakespeare's command of language here is remarkable. Shakespeare often operates on multiple levels of meaning, famously in his puns (like the title of "Much Ado About Nothing", a triple pun) and in exchanges like this one, where Shakespeare takes the confusion of his character and turns it into another jab from Shylock. Lancelot, in this scene, I had taken for an idiot. Someone who uses words that they don't really know the meanings to, but use anyway. I thought that the farther we got into the play, the more we would be able to laugh at him, in the same way we laughed at Dogberry. I didn't expect him to pretty much drop from the face of the Earth, as he does, and I didn't expect him to turn into a character more along the lines of Feste, from "Twelfth Night".
Feste was a fool, but he was no ordinary fool. He relied on his wit to provide humor, as often a good fool will. He was not a simpleton, as I thought Lancelot to be, but someone who may have been smarter and wiser than some of his superiors in the play. Take, for example, this exchange that he has with Olivia, the gentlewoman of the house, who has just bid her servants to "Take the fool away" (Twelfth Night 1.5.33). In the interests of making a point and not elongating things I'll sum some material up, essentially Feste counters and says that they should take Olivia away, for she is the fool. His reasoning:
Feste: Good my mouse of virtue, answer me.
Olivia: Well, sir, for want of other idleness I'll bide your proof.
Feste: Good madonna, why mournest thou?
Olivia: Good fool, for my brother's death.
Feste: I think his soul is in hell, madonna.
Olivia: I know his soul is in heaven, fool.
Feste: The more fool, madonna, to mourn for your brother's soul, being in heaven. Take away the fool gentlemen. (Twelfth Night 1.5.54-62).
He relies on reason to outwit his master, for the effect of humor. Certainly he is no fool, and Lancelot, in his own way echoes this kind of wit in Act 3, Scene 5. For example, his lines when he finds out that a Moor woman is pregnant, possibly with his child: "It is much that the Moor should be more than reason, but if she be less than an honest woman, she is indeed more than I took her for." (3.5.34-36). His twisting of words displays a kind of wit that I didn't think him capable of. I thought at first that he would prove a fool as in the definition as "one deficient in judgement or sense, one who acts or behaves stupidly, a silly person, a simpleton" (OED Fool, 1.A.) and not a fool as in the sense that Feste is a fool. To my dismay, however, before we really get to know more about Lancelot, he disappears. His final appearance is in 5.1 and that is only to announce the coming of Bassanio and Antonio.
So, is Lancelot a "simpleton", or like Feste is he capable of wit and if fact quite clever? I think the answer is that he is what Shakespeare needs him to be at the time. He's there for comedic relief, and to be a go-between messenger and further the plot in some points. He has some aspects to his personality, but he is in no way as integral a character to "The Merchant of Venice" as Feste was to "Twelfth Night". He doesn't even have the importance of Dogberry in "Much Ado About Nothing". In the end he plays only a small role in this play, and though amusing, is not essential to the workings of the play. In the end, I think he serves his purpose: to bring a laugh.