RE: converging multiple external source vlan access ports through IPS to another vlan on switch (pictures help explain)
I do not think you will be able to accomplish this with General mode and all untagged traffic. General mode can send multiple VLANs as untagged, meaning traffic going internal may reach its destination. But issues would arise with returning traffic as the General mode interface can only receive untagged for one VLAN.
Is the internal network all on the same subnet? Are the two ISP being used for redundancy, or providing connectivity to different groups? What model IPS device is being used? Does it support VLAN tagging?