I know speculating is (most of) the fun of what we do here, but I'm personally not going to worry about losing Tirado until A) he's left off the list and B) he's drafted. If perhaps before C) he's returned.
They were always gonna add some guys to the 40 via this kind of trade or waiver claims, just like last year. Also, if they do lose a player in the Rule V because of this (indirectly), but then trade Neshek at the deadline for two players, net win (particularly with the four months of work added in).
Other teams were interested in Neshek; it's not completely impossible the Phillies flip him before he even throws a pitch for them.
Trades are definitely going to be more fruitful for them right now; if Neshek was a free agent he wouldn't have wanted to play for the Phillies, and if he did he would have required at least a two-year deal.