I would try to limit it to no more than two locations, plus it will be hot hot hot!

Too hot, too crowded, and not enough time to be gallivanting around to a lot of places. Stick with Rome and Florence. Remember, your friend hasn't seen either before. If you think you'll be bored, just do a day trip from each place ( maybe Tivoli or Ostia Antica, and Pisa/Lucca or Siena). Venice, CT, AC, and Tuscan villages will have to wait until you have more time. I'd fly into Florence from Paris and back from Rome. Too bad about that return ticket thru Paris.

I would pick two places max and keeping where it's relatively cooler (mountains, north) in mind given you're going at a very hot time of year. If Rome and Florence are already on your list, I would leave them and just split the time between them without adding anything else (which you really don't have time for).

I will add to the pile of 'pick 2'.

What the 'other than Rome' place is will determine your to/from Paris travel choices.

I agree. Italy is bigger and things further apart than they seem. As your friend hasn't been to Italy, I would suggest keeping focus in the middle from Rome. Start in Rome and work your way up to Florence over the week. You can do that one of 2 ways - by the coast or through the interior. If you take the coast then you I would suggest going up to Pisa and basing there for a couple of days. From there you go see Lucca, a walled city worth a visit. You can also go a bit further up the coast and do the Cinque Terre on a day trip. I would also suggest a stop at Lerici along the way for the Bay of Poet. Then take the train from Pisa to Florence for a couple of days.

The other route would be to do some time in Rome and then go to Siena and base there for a couple of days. Siena is a lovely town and right in the heart of Tuscany. There you get to San Gimignano - the town of the towers, Montepulciano if you want to sample the wine or Montelcino which has a huge fortress. Then on to Florence.

You might want to consider doing an open jaw flight. Go into Paris and out of Milan. Open jaws are generally not more expensive and it saves a lot of unnecessary travel time.

Several options.

1

Fly Paris Orly-Pisa. 1H35m.

Train Pisa-Vernazza. 1H34m 2 nites.

Train Vernazza-Florence. 2H34m. 2 nites

Train Florence-Rome. 1H30m. 2 nites

This gives you a whopping 1 1/2 days in each location.

2

Fly Paris Orly-Naples. 2H05m
Then Curreri Viaggi Bus to Sorrento
1H20m. 3 nites Sorrento.

Train Sorrento-Rome. 1H10m
3 nites Rome. Edit. You could do a day trip to Orvieto from Rome. Train
1H17m

This is much more relaxing with 2 1/2 days in each local.

3

Fly ParisOrly-Florence. 1H40m
4 nites Florence. This gives you time for 2 days in the city and 2 day trips.

Train Florenc-Rome 1H30m. 2 nites Rome.

Fast, but feasible.

For air, look at Easyjet and Vueling.

For trains Trenitalia.com

Thanks - all good info I hate duplicating but I must consider my friend as well. Our tickets are bought already as we will spend our first weekend in Paris and last four nights of the trip in Paris - which gives us our six days Italy. I know it's tight, and thanks for all the suggestions.