As analyzing biological data with BioFSharp involves a lot of scripting, optional pretty printers help a lot when looking at results directly in the fsi window. This should be especially easy to add for parsing libraries that can already write the correct file format. A basic pretty printer for biocollections is already impelemented.
Here are some formats from the top of my head, feel free to add more

• BioCollections (BioList,BioArray,BioSeq)
• Clustal
• GFF
• FastA/Q
• GeneBank
• Alignments