Where, between the Ardennes and Wiltshire, do you intend to cross the Channel? That'll probably have some effect on the routes bods offer up for day four. I know some great roads to ride from the Ardennes to Calais in a day, useless though if you want to be in Wiltshire by 20:00 latest with the kettle on and the bike washed.
I pumped Radda in Chianti to Wiltshire into Google maps and guess that you'll aim to cross at Calais, particularly as you plan to come from the eastern side of France / the western side of Germany, perhaps? It's the way I'd probably go if I was coming from Germany via the Ardennes but, hey, we are all different.
The other thing Google maps told me (with a bit of pulling about to go via Como, Stuttgart and the Ardennes) is that it's a long way..... and you want bods to recommend roads to ride and come up with hotels? From Como to Stuttgart, you'll probably be crossing Switzerland. Are you a "I never take motorways and Swiss vignettes are a bloody rip off, mate" merchant? If so, you might well have a very long day ahead of you riding the 'must do' Swiss passes that some well meaning bods are bound to ping up and you'll still be many miles from Stuttgart. Similarly, you'll be buggered when someone tells you of great Ardennes roads to hoon (and chill) on, when you really should be hopping smartly towards the Channel and the safety of home. You'll get a long list (or a very short one) which will find you passing the front door of some obscure 'must do' German pension at 10 AM, rendering it useless or you'll be miles away from the next 'must do' hotel at 10 PM when it's peeing down and you've got a puncture. What has got you hellbent on Stuttgart? Is it a must do stopover as you must visit your cousin? Or is it just a large industrial city you've plucked at random?
Have a look at the sticky on Germany and the KurvenKoenig website. It's all in Kraut (I don't speak it either) but it's a wealth of ideas on roads to ride on a regional basis. Cut'n'paste at will.
The train solved your route problem on the way out; time for you to get busy, I'd suggest. There are loads of Ardennes hotels recommended on UKGSer already and a decent number for the Italian lakes. For Stuttgart, go to Booking.com and / or TripAdvisor.... good for the Ardennes and other places, too. Come on, you found your Chiantishire apartment, you can find hotel places that will suit you and your pocket the same way... and you can then find roads to join them up, surely? As to whether you need to add a day or two is up to you. Put your rough route from Chianti to your front door in Wilstshire into Google maps. Look at the distance and divide that by the number of days you plan on allowing for your return journey. Do they look reasonable for a daily average, when you want to stroll down to breakfast in your PJ's at 10 AM, plan on avoiding all motorways, definitely plan on stopping regularly for flower pressing enroute and be chilling with a beer in hand at four thirty? If so, great. No? Then change your alarm clock settings, hoon a bit (or a lot) faster and / or add a day or two, perhaps?
PS I know I recommend RiDE's routes a lot but, with a bit of imagination, they might help you. Mix'n'match some of their ideas into something that will suit you, perhaps?
PPS The bikermates that cross via Rotterdam enroute for Switzerland (and when coming back) will maybe take some more Germanly orientated routes. Have a look at their ideas, as you'll probably be wanting to go a pretty similar way, perhaps? That is until you head leftwards towards the Ardennes and on to Wiltshire.... don't forget to turn or you'll end up in Hull.