Here is the messy solution.
Tools needed:
http://www.freespacemods.net/download.php?view.77 (Click the download arrow)
1. Install Descent: FreeSpace into a new, different directory
2. Start that new FreeSpace up and then quit afterwards (don't make a pilot)
3. Open up qvp (the tool above)
4. Click File > Open and find root.vp in the NEW FreeSpace directory.
5. Go into missions, find sm3-07a.FSM, right click it and extract it somewhere
6. Open up FRED in the NEW FreeSpace directory.
7. Click File > Open and open up the .fsm file you just extracted.
8. You'll probably get an error, ignore it.
9. Click Editors > Ships, and click next until you're on the GTD Bastion (should be 4 clicks)
10. Change the Ship Class to GTD Orion (alternatively, GTC Fenris).
11. Click on Player Orders and check the Depart box.
12a. *Optional* See that GTC Gladiator in the Briefing Screen? Let's actually see it in-game! Select the GTC Gladiator. Assuming you're still on the GTD Bastion, 4 more clicks on Next will get you to the GTC Gladiator. Locate the Arrival section. Under Cue: you'll see it say "False". Right click on False > Replace Operator > Logical > true.
12b. *Optional* Due to how this will work, the medal won't be given to you, even if you destroy the SD Tantalus. So..., go to Editors > Events. Find Grant Medal. Click on the plus sign, then the plus on "when" and then the plus on "and". Right click on is-event-true-delay and select Delete Item.
13. Save changes whenever asked to do so and hit Ctrl-S.
14. Exit FRED and go back to qvp which should still be open to root.vp
15. Delete sm3-07a.FSM.
16. Find the new sm3-07a.FSM (That you made), and drag it into the qvp window (Make sure it's in the missions folder).
17. Click on the .. folder on top, go back into missions, find sm3-07a.FSM, select it, and hit the Add button.
18. Make a folder called Players in the NEW FreeSpace directory if it isn't already there.
19. Copy the Single folder inside Players from the OLD FreeSpace directory into the NEW Players folder in the FreeSpace directory.
20. Start up the NEW FreeSpace and play the misson.
21. If the GTC Gladiatior jumps in within 15 seconds, success.
22. At the end of the misson, tell the Bastion to jump out yourself (or anytime before).
23. *Optional* Copy the NEW FreeSpace Players > Single folder back into the OLD FreeSpace Players folder. Delete the NEW FreeSpace directory.
When I did this, I changed the Bastion into a Fenris cruiser, don't know if it matters. I also outright gave myself the medal, period. This should work.