A few points here:
What if the body, or most of it, isn't present? Or is Resurrection still a separate spell under this idea?
Also, to avoid the issue raised by the post after this regarding mystery solving - and some other headaches - I'd suggest raising the material component cost by at least 10x, if not 20x or more, for all versions except the very basic died-in-the-last-hour variant.
casting time: 1 action
components: V, S, M (300 gp of diamonds or diamond dust, which is consumed)
Returns to life a creature who has died in the last hour. The body must be present. Mortal wounds are healed, and the creature has 1 hp. If they died more than a minute ago, they come back with an additional level of exhaustion (max 5, even if they died of exhaustion).
Any Poisons and Disease or similar issue that killed a creature are not cured by this spell, but their effects are delayed for 30 minutes.
At higher levels: As a 4th level spell, works on a creature which has died in the last 24 hours for 1000 gp in diamond dust. At 5th level, a week for 5000 gp in diamond dust. At 6th level, a month for 20,000 gp in diamond dust. At 7th level, a year for 100,000 gp in diamond dust. At 8th level, 100 years, but requires the sacrifice of a legendary magic item. If the creature was dead more than an hour, day, week or year they come back with 2, 3, 4 or 5 additional levels of exhaustion (max 5).