TBH, I think you're just dreaming.
Probably the only engine in an F1 that can be upgraded in any meaningful way is the L Series diesel - although I don't know about the V6. With the K Series, you can tinker, and people like
@htr have done things to improve the engine for themselves - but they are not drastic improvements in power and take time and effort. There are more powerful variants of the K Series and they have been installed in Freelander - but they are not for the faint hearted, they involve engine swaps and a lot of effort and commitment - its not just a case of paying a bloke a few quid to do a remap. You have to be careful as well as the power delivery of those engines may simply not be suited to Freelander, with its size and function, and result in something that is not as good as the starting point. You also have to take into consideration what the engine is bolted to - ie the PG1 gearbox. When the PG1 is used in more torquey diesels or more powerful petrol units (eg T Series) its is upgraded and stronger - but you will have a standard K Series variant that Rover/Land Rover deem not capable of handling extra power.
If you then turn your attention to the running gear, you're options are just as limited. You can't bolt on 32" muds - the wheel arches are not big enough for a kick off, and even if they would fit, there is no low range box so the car would have terrible performance on and off road. About the biggest lift you can do is 2" - this doesn't enable big tyres, pulls the rear suspension out of alignment and will seriously impact the life of costly drive shafts. Once again
@htr can be your inspiration, he fitted uprated springs, they gave a small raise in height and a ride he is more comfortable with.
So, you saying "doing a complete upgrade of it mods etc" - what is it that you want to achieve? Is it really achievable or just dreaming?
You also say "it drinks like a trooper" - what are you getting, what are you comparing against and what sort of driving has given you this conclusion? A Freelander is not a small, highly fuel efficient, vehicle. It should be better than a full fat off-roader of the same era, but won't be as good as a small hatchback.