I recently published a new PDF on DMSGUILD adding some old, favorite, Spelljamming Helms back into the Dungeons and Dragons rules. In addition to the 17 Spelljamming helms, I included 12 powers you could add to any helm. Here are some more ideas I had for powers. One of the things I did was differentiate between the power source and the pilot of a Spelljamming ship.
Helm: This refers to any item that powers a Spelljamming ship. This includes items that are not chairs.
Pilot: This is the creature that controls the helm (or helms) of any given ship. This creature must be attuned to the helm of the ship.
Power Source: The thing or creature that supplies power to the helm and ship. When the power source is a willing creature attuned to the helm, it shares the awareness that a pilot has (see below).
Here are five other powers you can add to Spelljamming Helms, in addition to those in my PDF.
Hardened Ship
Cost: 50,000 gold pieces
When the helm is being powered, the ship has 20% more hit points than normal.
Maneuverable
Cost: 30,000 gold pieces
When the helm is being powered, a ship with a Maneuverable Helm has more Dexterity. This allows the pilot to move in tighter spaces more easily. In addition, once per long rest, attacks against the ship have disadvantage for one minute.
Sacred
Cost: 40,000 gold pieces
When the helm is being powered, healing spells are more powerful. All 1s and 2s are replaced by 3s.
Teleporting Pilot
Cost: 20,000 gold pieces
When the helm is being powered, the pilot of the ship may teleport anywhere on the ship as long as they can see the ship. A pilot can use this ability once per Rest.
Warded Helm
Cost: 40,000 gold pieces
When the helm is being powered, the all attacks against the helm and the power source in it have disadvantage. In addition the power source cannot be charmed, frightened, or otherwise controlled.
Don’t forget to check out my items on DMs Guild!