Very cool to see you using the BSP integration for Bazel. 
Interesting that -x objective-c is needed. Do you also need to set -x objective-c when building the project? If not, you shouldn鈥檛 need to pass it to SourceKit-LSP either. If you are willing to share extended logging without -x objective-c, I would be interested to see it to figure out what鈥檚 going on here.
-index-store-path should no longer be needed with SourceKit-LSP in Swift 6.2. I fixed that issue in If a build server doesn鈥檛 specify `-index-store-path` in the SourceKit options, add it during background indexing by ahoppen 路 Pull Request #2000 路 swiftlang/sourcekit-lsp 路 GitHub.
And finally regarding -working-directory, that also shouldn鈥檛 be necessary if you return a workingDirectory in the TextDocumentSourceKitOptionsResult as documented in sourcekit-lsp/Contributor Documentation/BSP Extensions.md at main 路 swiftlang/sourcekit-lsp 路 GitHub. Does that not work for you?