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Vines, ropes and such are possible is because it's easy to nudge the missile -7 to +8 pixels per scanline (or -15 to 0 without HMOVE lines) but in this case you'd need to theoretically position +/- 160 pixels, so you need the longer, general reposition routine that takes nearly a full scanline for a single object. And you have two objects

 

However, you could do something as shown if you allow 30Hz flicker (alternating between the upward and downward trajectory of the arc.) You may still need to alternate scanlines (or even every 3rd, 8th, or maybe 20th scanline), however, as you will either need a lot of RAM or do trajectory calculations mid-kernel, and/or use some very large or fancy lookup tables.

However, you could do something as shown if you allow 30Hz flicker (alternating between the upward and downward trajectory of the arc.)

Or left and right player's trails.

 

You may still need to alternate scanlines (or even every 3rd, 8th, or maybe 20th scanline), however, as you will either need a lot of RAM or do trajectory calculations mid-kernel, and/or use some very large or fancy lookup tables.

Without wind and friction, horizontal speed would be constant. But since we need to consider this, we would have to calculate vertical speed and position, plus horizontal speed and position. For two objects! I hardly can see how lookup tables could help here, so calculations mid-screen seem pretty much impossible.

 

So extra RAM seems to be the only possible solution.