Even though a patch will never come to the wii, here is a theoretical fix for assasin.

New Assasin:

Immune to UAV, Portable Radar, Heartbeat Sensors and AUAV.

Pro:

No red crosshairs or name when targeted by enemy.

Recon will be immune to CUAV, but not EMP.

Marksman users will still see the red name over assasin pro user's heads.

Every 3 scavenger packs refill a lethal grenade.  No more than 1 lethal grenade can be on the map at any given time by the same player.

New Blackbird Style killstreak that will show enemy players in realtime, but not their direction.  Will directly counter assasin.  Only in assault, and lasts 30 secs.

Why will this be more balanced:

None of the buffed perks will be overpowered, and the new blackbird killstreak will be a good counter, but cannot be easily reached due to only being in assault.  Assasin will still be a very good stealth perk, but it will have more viable counters.  Recon will still be effective under CUAVs, Marksman will be able to see assasin's hiding in bushes, and the thermal scope will be better than it is at the moment.  Also, the scavenger buff will also buff blast shield, because more explosives = more reason to be protected =  more blastshield = more competition for assasin.  Also, since no more than one explosive at a time, no more claymore spam. 

What do you think?