Part of the Pentagon's constituency, the Army and Air Force national guards, have added their voices to the loudening demand for simpler and cheaper weapons.

"The procurement of expensive, complex equipment to the exclusion of most other equipment has created a fundamental contradiction between what we have and what we need," a panel of guard officers complained in a recent report, "Vista 1999." The study group's mission was to figure out what the guards should have between now and 2000 and how they should be structured to back up active-duty forces.

For one thing, the report states in lamenting the trend to buy the best in weaponry, it is high time Pentagon leaders bought some inexpensive tactical warplanes to go along with the highly sophisticated F15 fighters, which now cost about $40 million each.

"Design studies by several aerospace companies show a more lethal, more agile, more survivable fighter than the A10" antitank attack plane "can be built for under $3 million fly-away," according to the report. The A10, built by Fairchild of Hagerstown, Md., costs about $18 million.

The Pentagon's penchant for fancy ground warfare weapons also handicaps National Guard units that receive them as hand-me-downs from the Army, the report says. "The national defense would be better served by providing the National Guard with lower cost weapons with proven here-and-now effectiveness coupled with higher reliability, reduced maintenance problems and procuring them in sufficient numbers to provide multiple battlefield coverage."

This is the same sort of argument the Pentagon's congressional critics are making as they try to force the military to trade quantity for quality on some weapons, with Sen. Gary Hart's (D-Colo.) campaign to force the Navy to switch smaller aircraft carriers one case in point.

The fear of passing ammunition to its critics may explain why the Pentagon has done little to publicize the 77-page "Vista 1999" report, described in the preface as "a long-term, no-holds-barred look at the scope, size, nature and methods of operation most appropriate" for the national guards.

The panel, chaired by Maj. Gen. Francis R. Gerard of New Jersey, stressed that the nation, assuming the draft is not reinstated, must turn to the National Guard to get the troops it needs for war. Therefore, units must be brought up to speed on the new tactics for winning by maneuver rather than relying on firepower, the report said.

Even counting active and reserve forces, today's Army "is inadequate in size and capability to execute the national strategy with reasonable assurance of success . . . in all the diverse areas of the world," the report said.

"Vista 1999" also says:

* A critical need exists within the Air Force to improve tactical air support for ground forces in direct contact with the enemy.

* The need for fast deployment and maneuver dictates that at least one "light, air-transportable" infantry division be formed within the National Guard.

* "Several" National Guard brigades should be trained and equipped to fight in specific areas of the world, rather than receive general training.

* Enough unattached National Guard brigades should be merged to establish two new divisions.