oh, this is going to be tricky, this is essentially asking for a way to force a “full onebox” somewhere on a link that is not at the beginning of a line. I think in very rare conditions like what you have here this may be useful.
I kind of support a change that would allow something like this for the ultra ninja cases where you want to force a onebox in the middle of a line:
<a href="onebox_url" type=onebox>...</a>
Trouble is all our onebox styling atm assumes it is the only thing in the line and gets full width so a bunch of assumptions would need to be changed.