I have taken some time going through the MUL and finding good units, comparing them to the new boxed sets, and using those available mechs to make good mech lances. Then adding infantry and vehicle support to make a full 350 army that will fight well. The first of these armies is available here. House Davion.

BattleMaster 1Gd
Thunderbolt 9NAIS
Shadow Hawk 2Ht
Commando 7S
Pegasus Scout Hovertank
Pegasus Scout Hovertank
Grenadier Battle Armor SRM Flamer
Grenadier Battle Armor SRM Flamer
Maxim Heavy Hover Transport (Clan)
Maxim Heavy Hover Transport (Clan)
Heavy Hover APC
Heavy Hover APC
Heavy Infantry Heavy Urban Response Platoon, 608th Lyran MTR, 3rd Lyran Guards
Heavy Infantry Heavy Urban Response Platoon, 608th Lyran MTR, 3rd Lyran Guards
Recon Infantry Recon Battalion, 201st Pesht Assault Team, 3rd Proserpina Hussars