i believe that Eurostar would be a good idea to add from st pancras to Ebbsfleet and fully making Eurostar st pancras and and also allowing the driving of trains that go further down hs1 but just to ebbsfleet
Apparently Eurostar are difficult to license, meaning it would be unlikely. Also only a few Eurostar services stop at Ebbsfleet so use there would be limited. Ideally we should get the line down to Ashford or even the Channel Tunnel (Not really my cup of tea though) so journeys would be longer. I don't even think Eurostar serve Ebbsfleet or Ashford at the moment anyway.
I reckon, and call me wishful here, the best courses of action for a Eurostar DLC are a loco pack for both SEHS and LGV, but other than that and maybe later on with a TER train a new route to Bourg Saint Mourice where Eurostar also operates in winter.
Really good idea but you might need to consider this DTG will need working switches for PZB LZB Sifa ATB EG NG ETCS KVB TVM-430 VACMA and Infrabel Memor II TBL for class 374.