So, how would you make Biggs more balanced from overly-defensive (as he will die anyway) to at least some offense so he can take someone with him?
I wouldn't.
For XXX I'd look at what Osoroshii says about Wes, Wedge & Luke. I'm the thread about Wes he goes into it pretty well.
If you really want Wes, Wedge & Biggs I'd still take Osoroshii's logic. Maybe something like:
Wes + VI
Wedge + R2 & Opportunist
Biggs + R2-D6 & Opportunist
This leaves 6 points for upgrades. Perhaps a proton torpedo to make Opportunist hit that much harder on the alpha. If the goal is keeping Wes / Wedge alive longer maybe add a hull to each. This spreads out protection ... protection that doesn't even come into play until after Biggs dies.
In Paul Heaver's write-up about his championship squad, he talked about using range and asteroids to keep Biggs alive long enough to shoot twice. Since you are talking about only using three ships, you need to deal as much damage as possible before losing one. Trying to make Biggs into a fortress doesn't do that in my opinion.