A working suggestion for reworking the Blender 2.80 VSE menus and additional functions within the limits of the two altered Blender-native python files: bl_ui/space_sequencer.py and bl_operators/sequencer.py.
Video tutorial: https://youtu.be/nN4xG3FMH-o
Download and place the two files included into these paths before starting Blender 2.80:
Download: https://github.com/tin2tin/blender_vse_reworked/raw/master/sequencer.py
Overwrite this file: 2.80\scripts\startup\bl_operators\sequencer.py
Download: https://github.com/tin2tin/blender_vse_reworked/raw/master/space_sequencer.py
Overwrite this file: 2.80\scripts\startup\bl_ui\space_sequencer.py
Download: https://raw.githubusercontent.com/tin2tin/blender_vse_reworked/master/vse_keymap.blend.py
Import the keymap: Edit > Settings... > Input > Import Key Configuration
If you want to contribute then start by taking a look at the New Features/Issues List. Is there something here you can help out with? https://github.com/samytichadou/blender_vse_reworked/issues
Share your opinion on what additional edit functions(existing python operators), which can be executed from the menu, should we add? Let us know here or on the VSE chat: https://blender.chat/channel/vse
Create and share a keymap for the new menus and functions(no coding experience needed): Some functions can be right clicked and choose "Assing shortcut" and other functions needs to be added or changed in the 'User Preferences > Input' menu, which also is where you can save your keymap so it can be shared. https://blendersensei.com/wp-content/uploads/2015/09/Create-Your-Own-Hotkey.jpg
Code clean up so it will apply with the Blender 2.80 python code guidelines. Most of the functions originates from other sources, so we need help to make it consistent, bug free and comply with the blender standarts for submittet code.
If you want to contribute and run the space_sequencer.py from the Blender 2.80 Text Editor you'll need to also open: "\2.80\scripts\startup\bl_ui\properties_grease_pencil_common.py" "2.80\scripts\startup\bl_ui\space_time.py" in the Text Editor to avoid errors.
For inspiration take a look at all the add-ons created for the VSE: https://docs.google.com/document/d/e/2PACX-1vSBzP9e0JbKlXa-oHJYxsUoFpvGsiPfeX5MXRdnQmKB55COr4J8JGw6orlJb6r0kjR0RMM3Jv4Vz_zX/pub