Whichever VLAN is untagged in HQ, where your ZD and HQ APs are located, is considered "VLAN 1" to Ruckus.
I assume that your 'guest1' WLAN in HQ, is putting clients on a tagged VLAN 4 from your initial description.
You didn't say if 'guest1' is using the Guest Access (with optional guest pass or no authentication, optional terms
and conditions, optional redirect to your choice or their intended URL after auth), or a standard WLAN with a simple
WPA2-PSK that you give to your guests?
If you simply wish to extend the 'guest1' WLAN to users in remote offices, you can enable Tunneling, which
will bring all their traffic back to the HQ ZoneDirector. This would support the Guest Access WLAN type that
I described above, or the standard type WLAN with WPA2-PSK, and you only need VLAN 4 at HQ, not at the
remote offices.
It will not "hurt" guests at HQ, just that their traffic goes thru the ZD instead of getting switched at the AP, but
you can extend your same WLAN to the remote offices, if that is your goal.
Is it the ZD's Guest Access webauth portal that you mean when you said "hotspot gateway", or an external
server that you want to bring remote guests back to?