The problem is, you rapidly need to apply a strong vacuum pulse after the joint has fully melted. Continuous suction simply cools the bit excessively and vastly increases the risk of clogging.
Done right, you'd need a vacuum reservoir with a volume at least an order of magnitude greater that the internal volume of the solder trap (filter) chamber and all the pipework, + a fast acting high volume solenoid valve to rapidly connect it to the handset, controlled either by a button on the handset or by a foot pedal. The vacuum pump can either run continuously, or be triggered by a pressure switch monitoring the reservoir vacuum.
I wouldn't give either of the unmodified desoldering irons shown above bench space, as I'd far rather have a normal plunger type solder sucker and a choice of irons to use including a 100W Weller soldering gun. All the manual desoldering irons I have used have had poor tip life and its a royal PITA keeping them well enough tinned to get good heat transfer to difficult joints. Its far easier to keep an ordinary iron's bit in good condition. The Teflon tip on a sucker is a consumable item, don't be afraid of letting it touch the soldering iron bit as you press the button, simply trim it smooth if it gets ragged and replace it if it gets too short/wide.