Syllie

When using the Add / Unify tool on two curves that share an edge, the result includes a bunch of redundant nodes, along that shared edge. Would it be possible to get a cleaner result from this tool?
To see what I mean:
Create a document with two overlapping curves, maybe a square and a circle. Unify them, and take note of the resulting nodes Undo that, now divide them Now unify them again. You should now see the nodes I'm talking about. I feel like 4 should give the same result as 2. Failing that, is there a way to automatically remove the redundant nodes?

Illustrator doesn't have this so if you implement this you can dab on them. Is that a valid argument? 

This is another request that seems simple, but probably isn't.
 
We use cubic Beziers to represent everything internally, including circles and ellipses.  There is no "pure geometry".  Due to this, we'd have to evaluate the curve to determine the potential tangents to a given point.  This can't be done precisely.  If we had true circles/ellipses we could precisely evaluate the tangents using the equation for the ellipse and tangent line, but this is a drawing program, not a CAD program.

Any chance of tangent snaps within a range of the cursor? This is super useful in CAD type programs like Moi3D which I use even for a lot of 2D stuff because of its snapping. I've attached a few screenshots to show how a line can be drawn and snaps are pre-highlighted, then the end result, and a practical use shown for a user interface design where two dials are joined by a background marking.

Like I said, you'd snap your direction first, then perform a second mouse drag while holding Shift to fix the handle length - then you'd have a perfectly symmetrical curve segment.
 
Demonstrated: SnapToReflectedPlusLength.mov
 
It has to be done as two separate actions, else you'd have two independent types of snap that would fight against each other. While it is another step, it means you'll have greater control over the curve.  Since we use Alt to cancel snapping outright, you might otherwise end up fighting against snapped lengths while all you really wanted was to fix the direction.

Ok, Here are some videos to demonstrate all the snapping that I've added for handles.  Please note, I'm not talking about snapping to grid, I am talking about snapping to useful construction angles relative to the opposite curve point and handle.
 
So, the following snaps are shown:
 
1) Snapping to smooth a cusped node - SnapToSmooth.mov
2) Snapping to inline, and 90 degrees to inline - SnapToInlineAndNormal.mov
3) Snapping to reflected angle - SnapToReflected.mov
4) Snapping to parallel direction - SnapToParallel.mov
5) Snapping to 90 degrees of parallel - SnapToParallelNormal.mov
6) Snap to logical triangle (useful for square corners?) - SnapToTriangle.mov
 
The useful thing about these snaps is that they will enable you to perform common curve construction, completely independent of grid or set axis.  You can use them in tandem with a second action while holding Shift to snap the handle lengths to match the preceding or following handle (while maintaining the direction you already snapped).