Firstly, you can't embed one Struts tag inside another. That's why it works for a regular <option> tag but not for an <htmlption> tag.
Secondly, using a message key for an option value is generally a really bad idea.
If this is an i18n application, the value will be different for each language. This means that in your Aciton class, you have to check for the value in each language to tell what action to take. Better to make the value a single string that is the same regardless of which language is being used.
The only situation where this would be useful is if you're storing the value in the database differently depending on the language spoken by the user. [ October 13, 2006: Message edited by: Merrill Higginson ]