Emulating iMac G4 with OS X Panther 10.3.9 on Intel iMac

Got a doobie of a problem.

So a client of the company I work in, who is an individual company designing and manufacturing industrial print textiles of some sort, has in their headquarters a room full of filing cabinets containing filed film negatives for these print textiles; there are so many files that they must be catalouged. Problem is, when the most recent catalouge was implemented roughly 15 years ago, it was designed to be a 15" iMac G4 with an 800 MHz PPC G4 chip and 256 mb of RAM running OS X 10.3.9 Panther and a custom-ordered/designed catalogue software application written specifically for this company and no other purpose (as in, it's not available for purchase otherwise). The software contains a huge database that is vital to the company to continue functioning; however, the iMac is predictably on its last leg and needs to be replaced very soon.

Optimally, we want to get them set up with a thin-panel 21.5" iMac running a quad-core i5 and 16 GB of RAM; since the database is contained in the old software, itself running in Panther, realistically the safest method would be to image the entire computer through Target Disk Mode and create some sort of emulated virtual machine within the newer OS, be it Sierra or otherwise; however, Panther was released before any Mac used Intel processors, and thereby is written in a strictly PowerPC-based architecture. How do I emulate that on a modern Intel machine? Any advice would be much obliged. Thanks!