RE: Shaft seals
You asked how common this sort of packing gland is..... It's a popular arrangement in Europe, at least on the canal boats. There they have a brass cylinder full of grease mounted on the bulkhead near the packing gland. A screw handle on the top pushes a plunger down and forces grease through the hose into the gland. The rule of thumb is to give the handle a half a turn at the end of every day's run. These boats also have the conventional packing nut/lock nut, too, in case the packing starts leaking too much. The grease is more for lubrication than water sealing.
To get rid of the waste grease you could dump it into the waste lube oil when you change engine oil. Some marinas like ours have receptacles for old grease as well as the big drums for old lube oil and hydraulic fluid.