Redirect to different Gateway?

once again, I have a quite special requirement. At home I have different VLANs with different purposes. To keep it as simple as possible, let's say I have VLAN 1 ( and VLAN 2 (

Now I have 2 Routers with interfaces in both VLANs:
192.168.$VLAN.1 is CRS326
192.168.$VLAN.2 is OpenWRT Cudy X6

Due to the performance of the devices and cabling structure I want to use the CRS326 as Gateway for all internal routing and the OpenWRT for Internet routing.

Therefore, I assign the OpenWRT (.2) as default Gateway and add static routes for internal network via CRS326 (.1) via DHCP Option 121 on the CRS326. This works perfectly on Linux and Windows PCs. However, the Android network stack seems to be quite shitty and therefore it does not work on smartphones, tablets and TV. They only have their default gateway and that's it.
As long as they don't need to access internal resources, that's fine. But as soon as they have to, they route their packets via .2. But the response packets are routed via .1 due to the static routes on the Linux server. Of cource, the SPI firewall on .1 will block them as it does not know anything about the connection.
The best and cleanest thing would be using the CRS326 as the only router for both internal and internet traffic, connect the OpenWRT to one of its ports and set it as gateway for internet traffic. However, this is not possible because the OpenWRT is both Access Point and WAN router, the trunk between CRS326 and OpenWRT is only 1 Gbit/s.

So, is there any possibility to configure the OpenWRT router that for example the destination address is not routed through the directly connected VLAN2 interface (which would of course be the default behavior) but redirect them to