Extension dependencies as weak dependencies

[Zetison]

If extensions have dependencies not present in the main project they must either be listed in [deps] or can be included in the extension i.e. (with EMGExt being an extension with EnergyModelsGeography)

[extensions]
EMGExt = ["GeoJSON", "GeoMakie", "HTTP", "EnergyModelsGeography"]

The former would require redundant dependencies (if EMGExt is not used) while the latter would in order to use the extension require not only EnergyModelsGeography to be loaded, but GeoJSON, GeoMakie, and HTTP as well. It would be convenient if these three packages would be loaded only when EnergyModelsGeography is loaded. Could this be implemented?