In fact, the father did "reinstate" the son to his former place - that is the significance of the giving of the ring and the sandals. Servants did not wear sandals, and would certainly not have been given rings. These gestures indicated the father's full acceptance of the son "back into the fold".
You are probably right that the son came home out of desperation... sometimes, that's what it takes to effect a turnabout in one's life.
Each son had something to learn... the father's love extended beyond what either considered fair or "expected".
As far as each "righteous" person is concerned, when it comes to God, there is good news and bad news.
The bad news is - we don't get what we deserve.
The good news is - we don't get what we deserve.