It all depends upon when you wish to sell it. Some people will like the hotted-up Celica, but don't expect to get back the money, time and effort you've spent on the car.
Some people may steer clear of such a heavily modded car. They think that it's probably been thrashed.
If you do it up to original specs then I'm sure you'll get much better value for money. These cars are getting old and rare - even the coupes (the liftbacks moreso) and a collector would pay a nice price for a pristeen original.
If your mods don't change any of the chassis, it is possible to keep the original parts and when you wish to sell the car you can either advertise the original parts are all available (so someone can bring it back to spec) or put the original parts on yourself and sell it as original spec.