Glad that most of you all appreciate the thought I put into this.
Bishop and TJ fill needs for the Blues, and with Parayko and Pietrangelo on the right side Shattenkik becomes expendable. The retention is so that the Blues can fit under the cap this year for a postseason run.
Shattenkirk potentially fills a need for the Lightning, Barbashev gives us a potential scoring line center who isn't a midget, and the pick evens up the value. The condition is there to protect the Blues in case their season unexpectedly takes a turn for the worse.
The way I see it, this trade is done with the idea that both Shattenkirk and Bishop are rentals and extensions are not discussed until after the trade. I think Shattenkirk holds more value than Bishop, plus the Blues are one of the few teams who really need a goalie this season. St.Louis may be the only team the Lightning can trade Bishop to, and there is no point in keeping him during a losing season.
After the deal, the Lightning have about a month to see how Kevin fits, contact his agent, and figure out if an extension can eventually be worked out. If it can't, than we trade Shattenkirk at the TDL, which should be significantly easier given the demand for defensemen.
St.Louis meanwhile have their own talks with Bishops agent. If the cost is too high, they let him walk. If he lowers his demand after a subpar season, the Blues can sign him after the expansion draft and then deal Allen.