1- There is no reason why I would want to open a plug-in window from hardware. If I am opening the window, it is to edit, which I would do on the screen in the first place.
It's very handy for those who want to quickly reference the plugin window without having to reach over to use the mouse. Live users have been requesting this feature for a long time.
2- Sure Maschine can be a Live controller, but then it is not having all the functionality of the Maschine software. It is disingenuous to tout both without mentioning they cannot be had together.
It's actually disingenuous for you to falsely claim that:
The advantage of Push is that it is not using a different software layer, but is directly controlling Live. At any moment I can switch to Live instead of being in the Maschine software.
when actually Maschine also directly controls Live without a "software layer". You can also switch back and forth between Live and Maschine at any moment.
Since Maschine only has a 4x4 grid, Maschine by itself is inferior to Push with its 8x8 grid. With Push, without having to switch pages, you have 8 tracks with 8 clips per track, plus scene launch buttons. Maschine you have to do multiple page switching to do this.
This is a very real advantage of Push over Maschine. As is being a 64 note midi 'keyboard' with ribbon controller. So to match these capabilities in Push with Maschine I also have to purchase a launchpad, plus a 61 note keyboard controller as well as Maschine.
Like I said, 8x8 grid is not much of a selling point especially at Push's laughable price point if you already have Live controllers like Launchpad or iPad controller like TouchAble, Griid, LiveControl, Lemur Mu...etc. or other iOS controller apps that do isomorphic grid layouts with scales.
The bottomline is that Maschine as an integrated software/hardware combo has very real advantages over Live and Push when it comes to things like the ability to have a completely mouseless workflow, having total control of pretty much every feature of the software, plugin automapping, exclusive Komplete preset support, a hands-on sample chopping workflow such as being able to sample directly to a pad, duplicate those pads, slicing, waveform editing from the hardware...etc.