So, I love when 40k makes new stuff (even if I don't manage to find the listed rules for it, and I haven't bought new Tau Codex), and am very interested in Commander Longstrike and his smallest-ever? crisis suit. One of the nice things, for me, is that "when is this happening" is practically irrelevant to this game; whatever new stuff they make can be implemented even way back when DW is occurring, perhaps just ignore a name, like Longstrike. I'm not sure how I would stat it, though, so I am asking for some ideas.

I don't know what he does in game, but I presume he increases his tank's BS, like Pask does, and read that he replaces the whole crew. So I was thinking something like this:

XV02 Experimental Pilot Suit
Movement: 4/8/12/28
Wounds: 20
Traits: Auto-stabilized, Dark-sight, Unnatural Strength x2
Armor: 7 All

Exceptional Integrated MIU: Deathwatch, p.178. This should cover his ability to pilot like a boss and the bonus to BS a "tank ace" should have.

I don't know what else, if anything, the suit should have/add. Any thoughts would be appreciated.

The only thing the suit actually does is allow Longstrike to fire a lot of overwatch, the boost the BS is due to Longstrike's Ace status. Background wise the pilot battlesuit has a great deal of computers and senors allowing Longstrike to use the vehicles AI in tandem with readouts from the entire battle.

I don't think there is a very good way to represent skill at overwatch with the RPG rules, though I suppose a bonus to the Overwatch action could do it.