I saw the "Mini-GTX" thread a bit lower on the page and I do belive that you could make a "solid" insert for Gamo Triggers. Just loking at you picture in the thread lower on the page, and with no experience with springers or their trigger groups I have made a crude drawing with paint that might be useful:
As far as I can tell neither of these would really sacrafice what I think are the important lines on your "Mini" and they are a bit more "solid". If it would work maybe you could even mass manufacture these peices in a cheap but strong enough metal (Aluminum might work?) and still be able sell the product at a cheap price? How much does a small block of aluminum cost, because if Steve thinks it has a posablility and no one else wants to try it in their trigger then I guess I will.