Feature request: Global base directory for configs, ROMs, saves and assets (NAS/network support)

Feature Description

I would like to request a feature that allows RetroArch to work using a single global base directory pointing to a NAS or network share (SMB).

The idea is to define one base/root directory, and RetroArch would automatically resolve all internal folders relative to it.

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Example (SMB / NAS)

Base directory: //192.168.15.150/RetroArch

RetroArch would internally resolve:

• ROMs → //192.168.15.150/RetroArch/roms
• Saves (SRAM) → //192.168.15.150/RetroArch/saves
• Save States → //192.168.15.150/RetroArch/states
• Thumbnails / Images → //192.168.15.150/RetroArch/thumbnails

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Use Case

This would greatly improve support for:

• NAS-based emulation libraries
• Multi-device environments (Android, Linux, Windows, TV boxes)
• Centralized backups and portability
• Users who want all RetroArch data stored on shared/network storage

Currently, each directory must be configured individually, which becomes difficult and error-prone when using SMB paths, especially on Android.

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Expected Behavior

• A single setting such as "Base Directory" or "User Data Root"
• All other directories inherit from this base by default
• Advanced users can override individual directories if needed

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Platforms Affected

• Android (SMB paths are especially painful to configure)
• Linux
• Windows
• Any platform using network-mounted storage

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Additional Notes

This feature would make RetroArch significantly easier to use in modern NAS-based setups and multi-device environments.

Thank you for your work on RetroArch.

No source file, test, or entry point is identified in the issue. Start by locating RetroArch’s existing directory settings and path-resolution code, then trace how Android, Linux, and Windows handle network paths. Done means one base directory supplies defaults for the listed folders while individual overrides continue to work.