This idea is a bit complicated but I was thinking - why don't the developers make a new fossil finding and collecting/mining system? Let's delete the fossil blocks and the permafrost. Then take the fossil models and make them brakeable only with pickaxe and able to stand in other blocks - like they are glitched but they aren't actually glitched. And last but not least let's create a fossil tracker or finder. And now how it works:
1: You craft this fossil tracker and start searching for fossils.
2: You find a Trike fossil under a forest [or its natural biome]. (This is just an example)
3: You start digging and find it.
4: You break all blocks around it and in it.
5: Then mine the fossil with an iron pick. (or higher)
6: The fossil drops all types of Trike bones.
7: Then you analyze the bones and get Trike DNA from them [70% chance of getting DNA; 30% chance of getting bone meal]
8: And the rest is the same.
So there are no more bio-fossils or tar fossils. And about the plants - I have no idea. Yet!
Sorry if there are mistakes.