Can I par-bake French bread?
I've never tried doing this with crusty bread myself (I've only par-baked rolls and such), so my answer is not based on personal experience, but rather what I know about the theory of par-baking, along with advice from Michel Suas in Advanced Bread and Pastry where he describes par-baking (pp. 163-167).

Anyhow, the brief answer is that you should basically do what your link in the question suggests: initially bake as usual, but cut roughly 25% off the baking time.  You should be able to get away with around 180F as minimum internal temperature, since the gluten structure should be stable at that point.  But you might need to experiment.  Ideally, the best par-baked results come when the bread is baked just until the structure is set and won't collapse during cooling.  

Since you bake at such a high temperature, you might consider lowering it just a bit to avoid early browning, but I would NOT recommend a "low-temp" par-bake.  That would inhibit proper oven spring.  I also would NOT recommend a "dry" par-bake -- assuming you already use moisture during your standard baguette bake -- since adding moisture to your oven in the first 10 minutes or so does at least five things: (1) it inhibits early browning, (2) moist air transfers heat faster, so it enhances oven spring, and (3) it keeps the crust soft and moist for a few more minutes, which delays hard crust formation and thus allows even more oven spring, (4) keeping the crust at a lower temperature for longer also allows increased enzyme activity which will ultimately enhance browning during the final bake, and (5) it helps create an attractive shiny exterior in the final crust. 

Michel Suas recommends high-heat par-baking for small or thin loaves (as in your case).  If you're having trouble getting the interior up to temp before browning occurs, you might consider either reducing your bake temp slightly (I'd perhaps try 450F or so rather than 550F) or venting your oven a bit after the first half of the bake to lower the temperature rapidly, and let the interior come to 180+F in the lower oven.  (Suas recommends this high-temp then low-temp approach particularly for larger loaves.  So if you wanted to make larger crusty "French bread" rather than baguettes, that might be more relevant.)

Basically, what you want to end up with at the end of a par-bake is a loaf that's exactly the size and shape of a finished loaf, with all the finished internal texture.  The only thing that needs to be completed is browning.  If you have inferior oven spring or internal structure during the par-bake, it will remain in the finished loaf.

You may have to experiment a bit with the re-heating step, but high heat and steam (to prevent moisture loss) are both generally useful.  Michel Suas also suggests baking on a perforated sheet pan rather than a hearth to avoid an excessively thick and hard bottom crust.

However, if you're concerned about bread quality for par-baking, what happens between the bakes is also very important.  Par-baked bread needs to be cooled to room temperature without excessive drying out (no fans or breezes around, since it's more vulnerable to moisture loss without sufficient crust).  And then it needs to be frozen as quickly as possible if you plan to store it longer than a day or two.  Any excess time spent in the range below room temperature and above freezing will degrade final quality and cause staling.



By the way, the reason I personally haven't tried par-baking with crusty breads is that I've read stories online of people who have tried it with somewhat inferior results.  It likely could work well for a baguette that you intend to heat and eat within one sitting while it's still a bit warm.  But without the commercial processes for handling (e.g., blast chillers to freeze bread as quickly as possible between bakes), the sense I get is that the bread produced at home just isn't as good after the final bake, particularly after it cools.  It can stale faster and the crust just isn't the same as a fresh-baked loaf.

This thread, with people who have actually tried par-baking and compared it to other methods, suggests the much easier approach of simply (1) bake loaf as usual, (2) freeze, (3) thaw at room temperature for a few hours or overnight, and (4) refresh crust by heating at ~325F for a few minutes.  I've done this too, and the result is very good.  And no worries about modifying recipes or gambling with getting the right doneness when finishing.