"could be complementary" is a correct and usable phrase in written English.
You can use it to suggest that two or more things may work together well to form a complete whole. For example: "The bright colors and the subtle textures of the room could be complementary."
"This could be complementary to formal child care," he said.
"It's all unknown at this point," he said, "but whatever is built could be complementary rather than competitive.
And while aides to Mr. Abbas say they are watching the Syrian talks with some concern, they acknowledge that the two efforts could be complementary.
"Why did they need to buy it?" Mr. Jovanovich said that National Computing's software programs for helping parents and teachers assess students' classroom performance could be complementary to Pearson's textbook business and online testing operations.
While some differences are only natural — an imam focused on religious activities planned for the center and a developer more likely to talk up the swimming pool — and could be complementary, they have sometimes undermined efforts to build support.
What Cage had in mind was a poetic perspective toward the music of the everyday — wind, traffic, sputtering bursts from a distant jackhammer — and a notion that simultaneous sounds, however disparate, could be complementary rather than contradictory.
"A lot of the offerings could be complementary to what we do," said David Grebel, president of the Association for Continuing Higher Education and director of extended education at Texas Christian University.
Parallel stimulation of alveolar edema resorption toward the interstitium could be complementary.
The user-generated QoS metadata could be complementary to the provider-generated.
Why? It's possible that Web and TV viewing could be complementary.
Biomass energy generation systems could be complementary taking into account their different properties in reliability.
