I doubt the bridge would lift as its a semi-hollow with a centre block. As long as the string tension on the neck is balanced with the truss rod tension should be fine.
I had never previously noticed the mini toggle switch below the bridge pickup on vintage starfires and as my modern flamed maple starfire II doesn't have one, I wondered whether I was missing out somehow.
I asked ChatGPT about this switch and it said:
The Guild Starfire bass is known for its versatile sound and high-quality craftsmanship. The purpose of the deep/hard switch on a humbucker-equipped Guild Starfire bass is to provide players with additional tonal options and variations.
The deep/hard switch typically offers two settings: deep and hard. When the switch is set to the deep position, it enhances the bass response of the instrument, adding more low-end frequency emphasis to the overall sound. This setting can be particularly useful when playing styles or musical genres that require a strong, deep, and pronounced bass presence, such as funk, reggae, or some styles of rock.
On the other hand, when the switch is set to the hard position, it alters the tonal characteristics to provide a brighter and punchier sound. This setting is suitable when you want your bass lines to cut through the mix or when playing styles that require more articulation and definition, like slap bass or certain types of rock music.
It's important to note that the specific tonal characteristics and effects of the deep/hard switch may vary depending on the individual bass, as factors like wood type, construction, and pickup placement can influence the final sound. It's always a good idea to experiment with the switch in different musical contexts to find the settings that best suit your playing style and musical preferences.
Regarding the earlier Guild bass models equipped with Bisonic pickups, they featured a different type of switch. The switch on these models typically had three positions: series, split, and parallel. The series position provided a full and fat humbucking sound, similar to having both pickups engaged in a humbucker configuration. The split position allowed you to use each pickup individually, providing a brighter and single-coil-like tone. Finally, the parallel position offered a blend of the two pickups in a parallel wiring configuration, which resulted in a unique and balanced sound.
In summary, the purpose of the deep/hard switch on a humbucker-equipped Guild Starfire bass is to provide tonal variations by emphasizing either the low-end frequencies (deep) or the punchy and bright frequencies (hard). This differs from the switch on earlier models equipped with Bisonic pickups, which allowed you to choose between different pickup wiring configurations to achieve various tonal options.