With IEEE802.1q VLANs sharing a gateway will not be possible.
(IF this product supports them) Asymmetric VLANs MAY be able to accomplish what you need, but there are caveats. Given you have servers which incoming clients are going to be requesting I am going to go out on a limb and say my assumption is that those caveats will be problematic for you.
This is an annoying subject, I personally despise asymmetric VLANs, and I recommend taking some time to research their potential benefits and drawbacks.
A gateway with multiple configurable "inside" interfaces (or that supports virtual VLAN interfaces) would be the textbook solution.