Taking only about the bike portion, SSB into HIM build can work well.
But why would you do the HIM if you target to fulls?
As an alternative, SSB2 is like a mini build. As your A race is later in the year, you could also consider taking another week off (during illness you don’t recover as much) and then start a full distance BBS cycle. Then you basically did a base-build-base-build-spec approach.
I would also consider where your weaknesses are and there’s some more important thing to work on?
Ok! What does the builder propose specifically for your HIM events A and B priority?
If the bike is what you plan to improve on, your in the right place. The SSB 1>2 into HIM BBS progression is an excellent combination for building bike fitness. I did it myself in the past and would very much recommend it.