The major changes President Carter will propose next year in the structure of the bureaucracy will be wide-ranging, and important, but they won't be as drastic as orginally planned or reported.

Insiders say the dozen-plus changes the President will propose in the government's makeup and personnel administration are taking final shape. The master blueprint - which has had nearly 700 career civil servants and political appointees helping with it - is almost completed. It should go to the President by the first of the year.

He's expected to make minor changes - having already approved the over-all design of the report - before attempting to put it into practice. Some of the changes can be accomplished by executive order. The major, controversial items must go through Congress.

Among the changes the President will propose:

A new corps for both career and political executives. It will be a high-risk, high-reward service - to be called the Executive Management Service. Contrary to early plans, and reports here, the EMS will not dip down into Grades 14 and 15. It will be confined to the several thousands supergrades in GS 16, 17 and 18 or their equivalents.

A new appeals systems that will make it possible for managers to fire more quickly and easily workers they consider incompetent.

A sharp reduction in the lifetime benefits given to military veterans. Virtually all veterans now get 5-point preference in test scores when applying for federal jobs, and valuable retention rights during layoffs. The Carter plan will not change any of the benefits for 10-point disabled vets. It will, however, cut back life-time civil service protection for veterans without service-connected disabilities.

Changes in the federal labor-management code, which dictate the way Uncle Sam deals with his million-plus unionized members, and organizations that represent workers who don't belong to unions. Although federal unions want a law (giving them new benefits and rights), administration officials prefer to stick with executive orders to set labor-management policy.

"The key to the whole program," a task force insider said, "is management control. Carter wants to be able to give orders and have them carried out immediately, not in three months."

Carter administration officials (and they have this in common with the first Nixon team) are convinced that government rules and regulations are one-sided, in favor of employees, making it almost impossible to straight-forwardly fire bad workers. Unlike the Nixon team, they do not seem to view bureaucrats as evil, partisan roadblocks.

Rather than characterizing federal workers as sloths to be poked into action and bent into shape, as key Nixon aides felt, the Carter people seem to feel that government workers are bright, honest and efficient but poorly led and, like overly protected children, not as beneficial to society as they might be.