General aviation pilot reported that to clear the runway at UAO the aircraft would need to cross Taxiway A without clearance; and suggested that the clear line be adjusted to a better position.

Narrative

Upon landing in UAO I taxied clear of runway on A3 and called Ground as instructed. I was coached/advised that in UAO I need to clear the yellow line designating clear of runway completely. I am well aware of this rule and would have; except that in UAO you cannot taxi across the line without entering Taxiway A; an active taxiway; without clearance.As there seems to [be] a lot of runway and taxiway excursions these days I feel this could create an unsafe situation. Taxiway A is well clear runway and perhaps the clear line needs to be adjusted to a better position. From where I stopped a B-52 could have safely passed behind me.As a retired airline pilot with over 27;000 [hours] I am well aware of the taxi rules; but I worry that a new or inexperienced pilot may go to another airport and inadvertently taxi onto an active taxiway. After I received my coaching from the Ground Controller; he then proceeded to coach another pilot who did taxi from an uncontrolled taxiway near the hangars onto Taxiway A. This further illustrates the need for changes at UAO.I hope this is taken as constructive observation and not a complaint of the staff at UAO.