In your
picture the armor seems mythical, I can do a version like it.
But what historical period does this chariot belong to? And do you have any carvings, remains or other visual guidance for historical armor for the period?
Dating
How the Mahabharata and Ramayana are dated (9th - 5th c. BCE ?) would help determine the beginning point of the heavy ratha's use. Their usefulness in battle was critical to the Battle of Hydapses (4th BCE). References to rathas as part of the order of battle occur as late as the 7th c. CE. So quite a long period is covered, which of course affects what armor makes sense for a unit.
Armor Type
Except for the two small bas-relief below, the only images I could find are from much later eras. Combined with the descriptions from various sources we should be able to develop a fair idea of what armor a kshatrya in a ratha would wear. Make sure to click through the thumbnails to the larger images for more a lot more detail. If anyone is interested a list of the several texts used in researching this could be posted. I apologize for misspellings in the subtitles, didn’t catch them until the last minute.

Bas-Relief Descriptions
It’s barely visible, but my impression is that the Barhut Stupa (2nd c. BCE) rider is wearing a rectangular breastplate on top of something else. Another relief at Barhut (no image available) is described as wearing scale armor similar to a find in Khotan. The statue from Peshawar (2nd c. CE) shows some kind of scale or lamellar armor. A closer look at the details of the patterning indicates that the torso is probably a curaiss - separate from the rest of the armor. The various close-ups below the two bas-reliefs and the other images are all Indian examples from later eras.
Vedic Era Descriptions
“The breastplate, known in Sanskrit as urastrana, has been in use in India from prehistoric times, and consisted of a single large plate covering the body from the neck to the waist. It was secured by four straps, generally of leather, which were fastened at the back. The breast plate came in several designs. It could be round, square or shaped like an eight-petalled flower. There were breastplates with floral designs carved in high relief, and ones with a pronounced ridge in the centre so that any edged weapon that hit the plate would slide off owing to the contour of the ridge.” - E. Jaiwant Paul Arms And Armour: Traditional Weapons of India. Rather than a full curaiss I take this description to mean a single plate covering the front - like that worn by the Barhut rider.
Harappan era: “A kind of scale armour prepared from thin domed pieces of copper perforated with two minute holes was worn as for protection, ...” R. C. Majumdar The Vedic Age
According to the Atharva Veda (10th c. BCE) the king - who rode a chariot - would wear a breast plate. The Rig-Veda describes charioteers as wearing breastplates and armlets. In other verses the armor is described as a corselet of metal. Both the Vedas and the Epics describe arm and finger guards used by archers.
Mauryan Era Descriptions
Arrian’s description of Porus’ armor at the battle of Hydapses River (326 BCE): “It was shot proof and remarkable for its strength and the closeness with which it fitted his person, as could afterwards be observed by those who saw him. But he was wounded in the right shoulder where only he was unprotected by mail, that place alone was bare during action, for his coat of mail being excellent both for strength and workmanship as it afterwards appeared, easily secured the rest of his body”. It is also described as embellished with silver and gold. Despite the translation as mail it sounds more like a sort of char-aina but with lamellar rather than plate. That would match the description of strength and the bare shoulders - also the close fit and flexibility for things like drawing a bow or swordplay. The pictured example of lamellar could be described as silver & gold.
The Arthashastra (2nd c. BCE - 2nd c. CE)discusses iron armor, especially breastplates.
Mughal Era
Some details of the Mughal Era plate & mail coats may provide clues to the armor of earlier eras. The shape of the plates is suggestive of how an urastrana may have looked. The "belt" gathering at the waist of the Tibetan outfit may be useful when thinking about corselet-style armor.
For The Ratha Unit
Keep in mind that kshatrya in rathas were the elite of the elite at any era. So they would have the very best armor available. Based on this research. The unit should be designed to cover as broad a timeline as possible to meet the needs of different scenarios. Imho, the riders should wear something like an urastrana or char-aina with bare arms. Whether a full breastplate, a smaller plate with straps worn over cloth or leather, or a lamellar corselet is open to interpretation - meaning unit-maker's choice. No skirting of the armor or leggings either, I think. Complete the outfit with arm-guards and a
helmet. Dhoti to cover the legs, of course, and barefoot or sandalled.