Yes, if he filled his Secondary Nature slot with a Centinger and his Tertiary Nature Slot with an Enrino, he could only take on their physical forms but not use their Natures. But the advantage lies in three aspects—Prana, Lifespan, and Transformation.
First of all, the Enrino had a Prana capacity of 1190 at maturity and a lifespan of 80 years. The Centinger had a Prana capacity of 3288 at maturity and a lifespan of 590. Virala's accumulation would be the summation of both.
He'll have a Prana Capacity of 4478 and a lifespan of 670 years. That was the first advantage. A sheer, physical advantage. Secondly were the transformations.
He could transform into a Centinger to varying degrees, in Stages, similar to his Empyrean Tusk form. There would be four Stages for his Centinger form. He could perform the same for the Enrino too, in four Stages.