The Assassin is the Assassin. That is, it is bad. Hard to make it even mediocre.
The new Assassin does offer option for multiple specialty ammo loads (up to 3, if you don't mind having only one shot of one type) and 5-tube launcher is better for many than just 2-tube one, but this isn't a big benefit overall. The Angel ECM may be useful if used for interference though naturally this means giving up stealth. But the Angel is easily found among Capellan 'Mechs anyway
Think the LPPC hurts the Assassin. The range is nice, but with the good mobility medium lasers tend to have enough range, so the weight could've gone to beefing up missile armament (insofar WYSIWYG RecGuide variant allows).
For high mobility, the Capellans have, for example, the Wraith and the Dola. For recon or missiles or general support, the Raven 5L or Raven II do fine job.