Interesting theory, however the Odyssey was rammed in the engineering hull
and the debris bounced into the starboard nacelle.
Ah, I see. Couldn't quite remember if it was the neck or the engineering hull.
Yeah. I was also a bit quick in my reply as I forgot to add that IMHO once the shields go down (or in Odyssey's case, "divert shield power to weapons") pretty much the whole ship is vulnerable. A neck hit, engineering hull or nacelle hit could be just as fatal or crippling against a powerful weapon or ship ramming into it.
It might be the opposite, where a lower-powered propulsion system could make her fast and not tear herself apart (we've seen small, low-powered ships hit high warp speeds like the Delta Flyer.) The Defiant's extra powerful power systems OTOH comes with a penalty of overstressing the ship.
So the ship could pump more energy into its engines than the hull (or possibly the Structural Integrity Field) could handle?
I think so / maybe.
There appears to be more detail in "The Sound of Her Voice" where the Defiant can push it to Warp 9.5 but only after diverting her phaser reserve power into the SIF.
Since Worf says the phaser reserves can be emptied, then it appears that the Defiant is unable to produce the extra power the SIF would need to protect herself above Warp 9 even though her engines are capable of going well past it.
BASHIR: We need more speed.
O'BRIEN: Speed's not the problem. I could increase the warp plasma ninety seven gigahertz. That would increase our velocity to warp nine point five and save us almost a full day.
WORF: The problem on the Defiant is how to maintain structural integrity when we go above warp nine.
O'BRIEN: Exactly. At those kinds of speed the ship literally starts tearing herself apart.
SISKO: Is there any way to strengthen the structural integrity field?
O'BRIEN: Not without bleeding power from some other source.
SISKO: Such as?
O'BRIEN: The phaser reserves.
WORF: That would be unwise. If we empty the defense reserve, we could find ourselves at an extreme disadvantage should we encounter a Dominion ship.
BASHIR: We're a long way from the front lines out here, Worf. The chances of meeting a Dominion ship are negligible.
WORF: We should not take that risk.
BASHIR: She'll die if we do not get to her faster.
SISKO: Use the phaser reserve, Chief. Give us all the speed you can.
O'BRIEN: Aye, sir. Thank you, sir.
On a rethink, her engines are overpowered but not enough to adequately power her SIF so a lower-powered system wouldn't help. So there probably are other factors at play that determine top speed and stress...