In my examples I use RX for the outer structure, which is unproblematic, as RX itself is not complex at all, and parsing it is easy, as easy as parsing brackets.

What kind of content you put into the blocks, depends on you. How you parse one block is independent from how you parse another block, which means embedding DSLs and so on is painless. You could view the content of a block as RX, but you can also just see it as plain text that you can parse however you choose.

This also means if you make a syntax error in one block, that does not affect any other sibling block.

The benefits of RX, especially at the outer level, is that all those ugly brackets go away, and all you are left with is clear and pleasing structure. This is especially nice for beginners, but I am programming for over 30 years now, and I like it also much better.

If you don't see that as a benefit, good for you!

If you don't allow the indentation based parsing to be nested within a bracket-based expression, it doesn't look too bad. At the top level you have the indentation-based parser. When that sees an open bracket, it recurses to the regular parser which doesn't care about indentation.