Trafalgar, Channel invasion pressure, and French commerce raiding

Was Trafalgar inevitable, and could the French conduct successful commerce raiding if they avoided major sea battles?

Commerce raiding was possible, but a Channel invasion strategy required fleet concentration and made a major battle likely.

France could conduct successful commerce raiding with individual ships, as it already did. Invading Britain required a different concentration of force: bringing the Mediterranean and Spanish fleets together, helping the French Atlantic fleet out, and then sweeping the Channel. Once those fleets attempted to contest the Channel, a major encounter was expected, although its location was uncertain. Abandoning the invasion objective would remove the need for that particular concentration and the battle it invited.