few players following me
Red Sox trade:
OF Davis, Rajai, $2m (2013)
OF Ellsbury, Jacoby, $6.5m (2015)
MI Scutaro, Marco, $4m (2012)
P Hagadone, Nick, $0.5m (P-n/a)

Tigers trade:
OF Crawford, Carl, $12m (2014)
OF DeJesus, David, $5.5m (2013)
SP Jackson, Edwin, $13m (2014)

I do this deal because i get a solid top hitter in crawford and dejesus who i feel can be another solid hitter  coming off injury and jackson a solid sp to help fill in sp needs

Yes... we need to... here is my suggestion.

We have a 50 GP and 40 IP rule for the establishment of the major league clock on prospect contracts.  Why note use those same numbers for position eligibility?

1) A minor league player called up from the EDR will immediately have their eligibility analyzed.
2) All players eligible for multiple positions will be analyzed at the trade deadline.  The rule can be 50 GP and 40 IP for the past and current season.  At the trade deadline, only the current season will count - similarly to how the 2008 rankings were phased out for contract extensions at the trade deadline.  Players hurt for the year may end up losing out on this, but they can regain position eligibility once they hit those numbers again.
3) Players are always eligible for at least one position.  If they were eligible for multiple positions and then became ineligible for such positions, positions will be removed in order of when they first became eligible for such positions in the first place.