Pilot reported observing an aircraft breaking off a practice approach turn into the path of an aircraft on downwind for an intersecting runway at a non-towered airport.

Narrative

DED has two runways; 5/23 and 12/30; winds heavily favored 23; and there were 2-3 aircraft in the pattern for 23. As I was crossing 30 on taxiway Alpha enroute to 23 I noticed an aircraft on approx. 5nm final. I queried them on the radio; 'DeLand traffic; is there someone on final for 30?' They responded 'Yes; DeLand Aircraft Y 5 mile RNAV runway 30; planning to go missed'. I advised that there were multiple aircraft in the 23 pattern/downwind that would be a direct conflict with their plan. They then replied 'Daytona Approach cleared us for the approach.' I advised them that approach clearance in no way gave them the authority to hazardously cut thru a full traffic pattern/intersecting runway. They then said they would be going missed early; to which I advised DeLand has an active parachute operation and that they should not overfly. Besides the fact that it would put them in direct conflict with the downwind traffic. They finally decided that performing a 180 turn and terminating the approach was the best idea; and while they did that they came within 2nm (1200') and about 400' of the downwind traffic. IFR rated pilots should know that on VMC days practice approach clearance does not somehow give them the ability to disregard VFR traffic pattern rules/right of way. Yet this is a repeat problem in DeLand; as I had the same situation around a month ago with a aircraft that I reported directly; in that case I was the traffic on downwind that was nearly hit. With all of the student traffic in this area it would be helpful if ATC added an additional advisory to their handoff radio call to CTAF. For non-IMC days; I would recommend that ATC amend 'Change to advisory frequency approved' to give instructions that include specific directions to avoid overflying the airport. Ex: 'It appears there are 3 aircraft in the pattern for 23; do not overfly the field; advise you circle NE to join downwind; change to advisory approved'. If this situation continues; it is only a matter of time before someone dies; again.