If you plan on training it, not really. Only train if he's 18 years old and trains near quadruple on hard (the best training I have seen is about 35% gain on stretching, 85% gain on cardio, and 110% on practice match).
There's two problems with training a special ability (or role):
- You generally need to hard train, so unless you have a ton of packs he won't be in your starting 11
- You won't gain any market value. This is horrible because 50 skill points is 2/3 of a star (a star is 75 skill points).
Buying an Shadow Striker outright from TL,
go for it. I did buy one outright too for my other team (Guide FC) and he score about 10 goals per 9 games
If you find he doesn't perform you should not have any issue selling him.