I’m not necessarily saying he can’t push 55 km/h over 10km, though even in slipstream those first 25km ridden at 55km/h mean he’s not exactly fresh at the start of his stint. And 55 may not be enough - we have no data what the average speed in the final 10km of that time trial was, for instance.Let me start by saying that i am not advocating he should do a 10km solo.
That said, since you're asking, you are severely lacking in your estimation of how fast Evenepoel can ride for that length. First of all, in the scenario you are discussing, he doesn't have to ride the entire length of the TT solo, just the final 10k. As for speed, on sections like those final 10k, he can push well over 55km/h. Look up his flat TT's (Vuelta'22, Vuelta'23, Giro'23, ECC'21... etc). After the climb it's downhill, which would actually suit him since speed is higher and his aerodynamics become more important.
He should try to keep Cattaneo and Van Wilder with him as long as possible, the three of them should have no problem going over the hilly section together. Someone like Vervaeke should completely bury himself on the climbs imho, since he won't be of much use later on anyway, probably more like a weak link by then. I think that it might be best to have Pedersen and/or Lampaert and/or Moscon go all out in the first split before the climb, to get a buffer. If one or two of them can manage to hang on til after the climb, that would be great, but they have to make sure they aren't holding back more in the first section in order to keep guys on board for the second section, than the advantage those guys will actually offer in the final section. I think that's the difficulty in managing this TTT, but Bora has similar problems with their line-up.
But more importantly, that tactic just doesn’t make any sense. It would if he was faster than his team. Everything else is just a final km or two where he gets to sprint…