Does beaver carcass make good Bobcat bait if so fresh or tainted better.

Fresh

… I prefer good lure to bait .. something skunky alongside something gland based

We do it a little differently in WA.
Hang it in the air with cameras

As soon as it is hit by the cat, pull the carcus and set a cage baited with beaver.

In Oregon I scatter beaver carcasses around likely looking bobcat areas and then come back in about 5 days and just set up the ones that have bobcat hits. No camera needed as the cats will almost always cover the carcass after feeding and will spend about 3-5 days feeding on the carcass. This help me save gas money on my line as when I set them up I know the cat will be waiting for me the next day if I did things right.

Domestic ducks work great too.

Bob Small from AZ had a interesting way to cage cats...

Yes