I have a 2007 Eddy Merckx Premium with 2008 Campagnolo Chorus shifters, UT compact (50/34) crankset & rear/front derailleurs. I want to throw this onto my Wahoo Kickr and make it my trainer bike. The issue is that the bike is a 10 speed, while the trainer has an 11 speed cassette. I have the 2017 Kickr, which cannot be used with a 10 speed cassette like some of the other models. I'd like to only upgrade what I need to get the bike to work on the trainer, so I don't need a cassette or new rear wheel with Campagnolo 11 speed compatibility. From what I've researched so far, it sounds like you can put 5-arm 11 speed chainrings onto the crankset I have now, and the 10 speed front derailleur will work with the 11 speed setup, but I'd like to know for sure before I spend any money, obviously. So that, plus a rear 11 speed shifter, 11 speed rear derailleur and an 11 speed chain should get me to where I need to be, correct? Thanks!
The simple, cheap way to do this using an off-the-shelf product is buy a 10-speed Campy to HG conversion cassette. Various options for this have existed over time; the only one I can see now is an IRD 11-32, which would work if you used the low limit to lock out whatever cogs on it the RD can't clear or that you don't have the chain length for. This is probably the way to go if you can stand the gearing jumps being larger than you're used to.
There is no technical reason why spacers for fully interchangeable/customizable cassette systems such as the Miche one couldn't be made to do this, and if they did exist then that would probably be the cheapest. I don't think they exist commercially, though. It may be possible to make your own with off-the-shelf spacers and microshims, once you figured out what the thickness needed to be.
To make the bike 11-speed, the answer is the chain and right shifter for sure, the front derailleur if you want good front shifting and minimal chance of chain drop, and then potentially the rear derailleur. The RD actuation ratio between Campy 10 and 11 didn't change but the capacity and large cog clearance numbers did in some cases, and you haven't told us your cassette range. If you then put a Campy 11 cassette on the wheel too, drop-in wheel interchangeability probably won't work between your Campy wheel and your trainer if you do this with its existing cassette unless you space out whichever is more inboard, at which point drop-in interchangeability won't work between various wheels if it's the wheel cassette that needs spacing, or between the trainer and different bikes if it's the trainer cassette.
To my awareness there's no right Ergo you can buy here that doesn't leave you with a tactile mismatch. 11-speed index rings that fit into your right shifter were never released.