Is the number of people using travel agencies (online or off) holding up? Personally, I haven't used a travel agent in over 10 years, and I travel a lot. Flights are all booked direct with the airline online. The same with car rentals. And hotels are usually booked using laterooms.com.
Maybe you'd be better looking at new ways of selling travel, rather than duplicating the old ways that are declining. I think the days of all in one shops will soon be in the past. Flights, hotels, and car rentals (the main purpose of old time travel agencies) are all very different fields. How about focusing on 1 of these, or on niche travel?