I can relate to this thread.
I have two trains of thoughts on this.
Firstly the R: This is a car that has come of age with the mk7. I ordered my mk7 GTI knowing that VW had pulled all the stops out with the chassis design and the vast torque improvement with the engine makes it a true joy to drive - the turbo spools up beautifully and it is a very smooth and tractable engine, reasonably economical, punchy, covers ground really quickly... I could go on.
When the GTI was released it was clear they'd made a big effort to make it a huge improvement over the old mk5 chassis which was quite a feat as this was a very competent car in itself. The inside of the GTI is like home from home - lots of detail improvements over the mk6 but still giving that familiar feel and excellent driving position. VW were saying that following poor 6R sales they might not even import the mk7 R.
Alas, when the 7R was released about 9 years after the mk5 GTI it seemed to hit the same spot that the mk5 GTI hit back in 2004. It was a huge step up over its predecessor and had masses of reserve in both engine and chassis. VW dropped a b0ll0ck by releasing a load of cheap lease deals, thinking it would generate sales of a slow seller, and get it out there on the streets (using the benchmark depreciation of the mk6 R to bolster low monthly payments for the mk7 R) at around the same time as the press cottoned on to the 7R's massive chassis potential and 'good value' at being bang on £30k for a 300 bhp hatch (with 4wd); which is a pretty attractive package even if it doesn't have the prettiest of faces.
I think the 7R is the new mk5 GTI.
Just like the mk5 GTI there will be two schools of buyer - those that want the performance for the price who will keep the spec low, and those that want a small car but have heaps of cash so will go heavy on the options. Both cars will have their market and so long as you don't expect the same return on a zero spec car (which is hardly utilitarian) as one with four grand's worth of extras then you'll be fine, it will be a desirable car for years to come (just like a mk5 GTI).
Those are my thoughts on it anyway, I could well be wrong.
Now on to my pet subject, modifying your GTI without going silly.
Regarding the TD1, you CAN remap but just make sure it's a decent one and that you're prepared to go in and pay the labour rate of the tuner to remove the map before dealer visits. If you break down miles from your pet tuner then you have a bit of a dilemma on your hands! But there would be ways around that.
Personally I'd play safe(r) and get a tuning box.
Having said that, just running a DTE pedal box from DTUK really brings the GTI's engine alive without touching the power output. Try one, you might be surprised.
Springs? I've spent 30 years messing about with GTI suspension and have come to the conclusion that in all that time and with all that money spent I've only ever been happy with about two sets of aftermarket springs I've owned and even then they had drawbacks.
I'm older and wiser now, and unless you're going to drive on track (which I occasionally used to) then the suspension on the modern GTI's are pretty darned good as standard, aside from the damping which could be improved upon a bit. If you fit lowering springs be prepared for at least a bit of harshness. I'm fairly tolerant and run aftermarket suspension on my other car and even that gets on my t1ts a lot of the time.
The suspension/chassis on the PP GTI is basically the same as the Leon Cupra which is the car that became famous for the sub 8 second 'Ring lap - despite all the plaudits for the Golf R, the standard GTI suspension is an amazingly accomplished bit of kit for what it is.
A modified downpipe can throw a TD1 just like a remap and you'll get no real gains unless remapped to take account of it. The main gain of the downpipe would be quicker spool but with less back pressure I'm sure the ECU will log something and it's not something you can easily hide from a dealer.
APR intake - how much time do you spend with your bonnet up looking at it? Waste of money IMO unless you have a map that makes use of its abilities to flow more air.
Fast road pads? How hard do you drive? They wear quicker and tend to be quite dusty.
UPrated ARBS - I like that idea.
Uprated mounts - depends on side effects!
Wheels: I have a friend that is pretty serious about his modding and he swears by OZ alloys as they're light and pretty stylish. However he does a bit of track driving and does say that the OZ's bend easily when used as a road wheel.
Personally I'd go BBS on a German car (and did for a while).
Spacers make the standard wheels look a lot better.
Michelin PSS: now we're talking. Quality rubber.
Only fit parts that are easy to take off again when you sell the car if you want to minimise depreciation. Don't go mad with mods, it's a fast changing world out there and you might find VW release a more attractive GTI in 12 months time, either that or the R will suck you back in.