The levels will work, but....
1) The HS2 viaduct is high, very high. About 20 m above ground level as it passes the Freightliner depot. There isn’t enough space from the end of the ‘throat’ for such a curve to dive down, as the bridge over the Aston line and the River Rea are constraints. Therefore the connection must go up and over.
2) it would need to start almost exactly as the line crosses the Aston Line, and swing up to maximum gradient immediately in order for the ‘SW bound’ track to get sufficient height to cross HS2 itself. (Unless, of course, it is to be a flat Junction?)
3) this viaduct would be around 30m above ground level, then start curving round to cross HS2, the Freightliner depot and cranes (interesting challenge that, not sure if its even possible), then transition to maximum gradient down whilst crossing the Derby line, the WCML and the Camp Hill line before dropping down to meet it somewhere in the region of St Andrews. It would need the permanent closure of Garrsion Lane, St Andrew’s St and Emmeline St plus extensive demolition of residential property and probably (hopefully) St. Andrews itself.
It would be a bit easier if it was a flat junction at the Curzon St end, but still need residential demolition.