[X] Make it an infirmary. Remembering Esmeralda's office, set up an operating table, arrange the supplies you took from her, and turn this into your own medical space.
All options would look nice, but this one is as much a training room as it is a memory and a military asset... As much as I would love to see Las Noches tear itself appart for no apparent reason before the main conflict, having an infirmary is too tempting a choice.
And apparently we are at the limit of the power curve, more variety of mundane skills is a nice luxury that can be afforded.