How can I improve recovery time of my hot water baseboard system?
You could investigate adding additional baseboard heating units in each room either longer if there is room or double stacked units.  You could adjust the boiler water temp to 190/200 to increase the heat output of the existing baseboard units. If this were my problem and I didn't know what to do I would call a professional and ask for recommendations. Knowing what to recommend from a statement made or question asked is difficult since no one can see the house, the floor plan, or the actual installed equipment. There may be a lot that can be done to help but actually being at your residence would allow for the best outcome. If you could, post pictures of your location, situation and the installed equipment for better suggestions