Every time I launch Obsidian it should land on the same page.
Setting in preferences that defines a default landing note page (existing one, or then created when defined). It should be overridden when the obsidian:// URL syntax is used bypassing the landing page.
See above
Hacking alias launches in Windows and MacOSX to accomplish this, someone needs to know how to set that up.
I too would like to see this.
On a related note (and maybe this should be a separate feature request…), syntax that shows a list of workspaces that can be clicked on would be neat–right now I don’t think that workspaces get the “marketing” that they deserve within Obsidian and I’d like to see that change. 
I agree a setting in the preferences that allows you to choose as described above, but while also retaining possibility of the current behavior.
I would support this. I would like to open to an Index page or an MOC.