Amusingly the Lahaina Bypass (HI 3000) has limited access elements and is going to be extended southward. While unlikely it isn’t totally unfeasible to envision the corridor eventually tied off closer to actual freeway standards.
Likewise, HI 3800 does have a partial interchange with Kala Road and only one major at grade intersection with HI 36 east of Dairy Road/HI 380. I could foresee a situation someday where it would be desirable to grade separate HI 3800 and HI 36.
Interesting to note, HI 3800 is multiplexed along HI 380 to the junction of HI 3500/HI 311. I assume that signage was placed given it gave traffic a single route to follow back to Kahului Airport. My thought when I saw it was to truncate HI 380 just to Dairy Road and extend HI 3800 to HI 30.