Is it legitimate to create different HTML files for different keywords and redirect the URL to the homepage, for all of them? I would write different meta title and description for all the keywords. Does it hold any importance from SEO point of view?
Meta tags in HTML is a very important role, it is also supported and SEO attribute importance to the crawler track your website.
if you want to create separate page for separate keywords, then that will be great. that will give you more pages on your site and your link building will be diversified and more natural as well. however, i wouldn't recommend you to create separate pages just for the sake of redirecting to the home page. this is not natural and google will know your intention very easily.
I completely agree with @sultanofseo, creating pages intentionally and re-directing them to home page is not a good practice and not a advisable. As said google has certain stats to redirect all the juice of old page to a new page (that is why google takes time to pass juice of old to new)...
If you do any such CLEVER sort of thing in very small amount, it may help you, but you try to make it a habit and try to dodge Google, I bet you are going to get really hard hit from Google!
Keywords in HTML are words that you are targeting on a web page. They are typically short phrases that represent what the page is about. They are also, hopefully, the words that someone might type into a search engine and find your page. If you are going to include meta data on your web pages, you should ignore the keywords tag, and instead use the meta description tag. This is meta data that nearly every search engine uses to describe your web page in their index. And that extra information could mean the difference from a customer clicking on your site for information or someone else's.
I also agreed with sultanofseo. If you want to redirect all you pages to home page then its not worth to have different pages for different keywords. Please don't do that. Instead use your different urls for SEO and link building and get better results for specific keywords.
You can set the keywords in to metatags of any page according to that page title and page information. for eg. you have keywords like web development, web development company, .Net Development, Internet Marketing, Best SEO Works, Web Site Development Company etc. Now keywords like Web Development, .Net development are you can set on the inner-page like web-development.aspx or web-development.php Other keywords like web development company, Web Site Development Company are set on home page. You can also set the keywords in to content of that inner page and also set the link of home page on those keywords.
do not make separate pages. just put meta titles etc on same page . for different page put different according to new page.