If a Jabari challenger for the Wakandan crown had won in the ritual combat and been made ruler, would they still receive visions and power of the panther goddess Bast, or from their own Gorilla deity, and a different suit matching that theme? Answers from any canon would work, since this scenario is not seen in the MCU
I'm basing this answer on Earth 616 (the main Marvel comics continuity).
It is apparently the 'Heart-Shaped Herb' that is said to link the Black Panther to the Panther goddess Bast [Black Panther Vol 4 Issue 2], although there is apparently a scientific reason for the increased strength and senses that the herb gives involving a mutation of the plant from Vibranium [Black Panther Vol 3 Issue 1].
Anyone who uses this herb who is "not worthy or of noble blood" would perish according to Wakandan folklore [Fantastic Four Vol 1 Issue 52].
This is partially backed up by the attempt of Klaw to use the herb, who almost perished in the attempt [mentioned in Black Panther Vol 3 61].
So to actually answer your question (if this scenario took place on Earth 616), the Jabari challenger wouldn't actually gain the powers of Bast (via the Heart-Shaped Herb), instead it would make them very ill or possibly kill them (unless they had close blood ties to the royal family, which I can't find any reference of).