What are these bridges made of? Wood? I tend to picture bridges made of stone, concrete, metal or a combination thereof.
Fire can still destroy things made of stone or concrete if it gets hot enough.
some fires fueled by cerosin are known to melt steel beams
Ignis pessimus delet pontem should be fine
The best thing about Latin is that its complex, well defined suffixes allow you a lot of freedom to put words all over a sentence if you so choose.
That being said, it's preferable that active verbs go at the end of sentences.
Idem for: pessimus ignis pontem delet!
Just report the alternative word orders that aren't accepted yet.
The order of the latin words should be a bit flexible. It is better to know the latin if you have to teach it.