All that is needed is an extension very much like the adapter Seneca Woodworking makes for the XL that permits the use of bits for the 500.
The length of the adapter would have to be tuned to achieve the correct mortise width.
You'd make a normal plunge to max depth using max width. Then add the extension and reset to the middle width setting. You'd need to have it powered off to place the machine for the second plunge because the end of the bit is out past the face of the fence. Power on then plunge
The negatives are obvious. It's tedious and there's the risk of breaking something. But the positive is pretty huge, 100mm long tenons for mortises cut with your 500. There's the old adage, don't tell me what it was designed to do, tell me what it will do.
The length of the adapter would have to be tuned to achieve the correct mortise width.
You'd make a normal plunge to max depth using max width. Then add the extension and reset to the middle width setting. You'd need to have it powered off to place the machine for the second plunge because the end of the bit is out past the face of the fence. Power on then plunge
The negatives are obvious. It's tedious and there's the risk of breaking something. But the positive is pretty huge, 100mm long tenons for mortises cut with your 500. There's the old adage, don't tell me what it was designed to do, tell me what it will do.