Seems a bit dumb as a business proposition. If one existed within 90 minutes of me though, I'd love it.
1) Why not rent out or buy an existing race car track? There are tons that go under every year, and most of them still have their pavement in good shape. Find one by a lake, and some bike trails, and you're done.
2) As mentioned above, the lack of variety could get boring
3) Would only really work for Olympic and shorter distances (who would go to a purpose-built facility and still put up with doing multiple laps?), which means you miss out on the "I have more money than god" HIM and IM crowd
4) I'd think they'd have to have the thing booked pretty much continuously to make any money on it.
4.1) A normal tri needs to pay for cops, road closures, and rental of whereever transition is for 1-2 days.
4.2) This place needs to pay for its lake, roads, landscaping, buildings, staff, security, year round
4.2.1) Although the insurance might be a little lower because of the controlled race environment (no cars, no boats, better lifeguard amenities)
5) Aside from world-class events like ITU races or the olympics, is there actually demand for spectator slots at a tri? Triathlons can be fairly boring to compete in (especially Oly/HIM/IM), let alone watch.
Things that'd be cool:
1) This place could have a variety of races every day of the week: crits, OW swims, runs, triathlons, duathlons, etc. If you lived near it, your training could include tons of races in many disciplines, which I think would be fun. They could sell a season race pass and you could just show up for everything.
2) Closed course means no worrying about cars coming, reduced getting lost.
3) They could probably "grow the pie" by causing intermingling of various sports specialists. Crit people could try out dus, triathletes could try out bike racing.
Again, I'd love for it to exist, but I can't see how it would stay solvent.
STAC Zero Trainer - Zero noise, zero tire contact, zero moving parts. Suffer in Silence starting fall 2016