I have two Kalkoff include i8 bikes and use the VW T6 two bike tilting towbar rack, it works fine as they are very heavy, there is a Thule equivalent. I tried a few to get the most useful, as far as I can tell there is no way to get in the back if you have bikes, I tried the several including Thule that are supposed to give enough room to open the tail but its not enough. Kalkhoff bikes are great, and the battery is good for 100 miles plus.
A couple of years ago I spent a great deal of time trying to find a solution to the same problem as posed by Mark Masters. I had two Kalkhoff e-bikes, each weighing about 22kg. and a Westfalia detachable tow hitch.
Initially It looked as though the Altera Strada DL3, which has a "slide away" mechanism which would definitely clear the tailgate of the Cali., would fit the bill but it wasn't capable of carrying the weight of the two e-bikes. I asked searching questions about bike carriers offered by Westfalia and Uebler but no manufacturer or re-seller could provide me with an assurance that their products would tilt away from the back of the vehicle sufficiently to clear the Cali. tailgate.
I eventually bought a Thule EC G6, having tried it on at a re-seller and been persuaded that it did what I wanted. I subsequently discovered that the re-seller's guy who fitted it onto the towball had not mounted it quite correctly and that when correctly mounted, and with bikes in place, it did not tip backwards sufficiently to enable the tailgate to open fully.
I have replace the stainless steel rope stays (which attach between the fixed and moveable element of the carrier with an eyelet in each end of each stay) with slightly longer ones. The replacement stays were ordered from S3i Group, 1 Faraday Close, Snape Lane, Harworth, DN11 8RU. The precise detail of replacement stays (as invoiced) is "3mm Eye-Eye Assembly - 7x19 200mm Pin Centres". The delivered cost of the replacements was £36.79 (incl. VAT).
I'm sure that my replacement of the stays which were fitted to the carrier as purchased will have prejudiced any Thule warranty but the solution works perfectly and the carrier (with e-bikes mounted) can be tilted back to allow the Cali. tailgate to open fully. I'm very pleased with the result.