The prosecution's request to drop the most sweeping and controversial Iran-Contra charges against Oliver L. North could make it easier to put the former presidential aide on trial, legal experts say.

The most politically explosive charges, alleging a conspiracy to divert to Nicaraguan rebels $14 million in proceeds from U.S.-Iran arms sales, will be gone if the dismissal move by independent counsel Lawrence E. Walsh succeeds.But some experts say that would leave a "lean and mean" case against North, free of problems that have bogged down the proceedings for months.

District Judge Gerhard A. Gesell will decide whether to grant the dismissal motion. If he does, prosecutors will still be able to try the former National Security Council aide on 12 felony charges, including allegations that he shredded documents and lied both to Congress and a presidential inquiry in an effort to conceal his involvement in the Iran-Contra affair.

"The sex appeal part of this case is always the conspiracy," said Washington attorney Stanley Brand. "But there is still a substantial case left."

"Lying to Congress and obstruction of justice are not small matters, if in fact that's what happened," said Brand, a former counsel to the House of Representatives.

"Lying to the Congress may be worse" than actually diverting arms-sale proceeds to help the Contras at a time lawmakers had banned such assistance to the rebels, Brand said.

"The public's perception of this and what it says about the distribution of powers among the branches of government is as important to me as whether anybody goes to jail," he added.

The remaining counts carry prison terms totaling 60 years. They include charges that North lied to Congress in 1985 and 1986 about his involvement in the covert Contra resupply operation.

North also is accused of accepting installation of a $13,800 security fence around his suburban Virginia home, pocketing at least $4,300 in travelers checks from Contra leader Adolfo Calero and illegally using a tax-exempt foundation to raise money for the rebels.

Other counts charge that North lied to Attorney General Edwin Meese III and destroyed official documents during the Nov. 20-23, 1986, presidential investigation of the Iran-Contra affair.

Since the indictment was returned March 16, a number of federal prosecutors have privately criticized Walsh for bringing a broad conspiracy charge against North and his three co-defendants.

These prosecutors questioned the wisdom of trying to criminalize the conduct of North, former national security adviser John M. Poindexter and arms dealers Albert Hakim and Richard V. Secord.

But many of these same prosecutors also supported the decision to charge North with destroying documents and lying to Meese.

The Justice Department last fall filed a brief criticizing a legal theory Walsh used to support the conspiracy charge, saying it would set a dangerous precedent for prosecuting government officials whose conduct had not actually violated any laws.

Walsh's decision prompted charges that the Reagan administration deliberately held back releasing some secrets to help scuttle the major charges against North.