I think that the biggest thing that scratch could improve is it's custom blocks, here are some improvements we could make:
1: Custom Booleans.
2:Custom reporters
3: Custom c shaped blocks
4: Drop down menus as inputs

Here is how these would work:

1: Custom booleans– These would use a report block to report true or false in diffrent cases. If the report block was deleted it would report false
2: Custom reporters– these would also have a cap report block to end the code, the report block would accept variables text and numbers
3: Custom c shaped blocks– These would have a script block, which would use the script inputed in the c block
4: Custom drop downs– In tye first drop down menu there would be an otpion to add a drop down menu and options to add more entries and program them with certain inputs

Note: any mock ups would be appreciated, if someone wanted to help

This is likely the best place to discuss “better” custom blocks: https://scratch.mit.edu/discuss/topic/20661/

This way all the discussion stays in one place.