Is it possible to merge 2 dvd's and keep all the content, menus and everything?

I'd like to back up 4 episodes of Farscape onto one dvd and keep the menu's and extras. Is there an easy way to rip 2 dvd's, merge them into one, add a 'select title' menu without having to re-author the whole dvd?

I've been just ripping the individual episodes, making mpg2s and creating a new menu and re-authoring the whole dvd. Obvious if I did merge 2 dvd's I'd need at least one new menu to select which dvd title to goto. But it would save alot of time if I didn't have to re-author the original menus. Is this easily do-able or even possible?