Besides Lilithmon, I choose Cherubimon to be another LV6 for the deck. The Cheribumon "when digivolving" effect can be used to play either Yamato or Koichi tamer cards, there is no play-cost condition for the tamer that can be summoned from trash by Cherubimon's effect. Except for Rookie Rush deck, the opponent normally does not have many LV4 or lower digimon in the field, so 1 or 2 tamers are good enough to clear the opponent's board. It is useful to deal with blocker or "retaliation" LV4 opponent's digimon.
For Cherubimon "On Deletion" effect, Neemon and LV3 Lucemon are candidates to get back from trash. Lucemon gives "Recovery+1" and Neemon's "On Play" effect credits you to play a Koichi tamer for free.
Koichi is very important to be recycled from the trash. First of all, you can "draw 1 trash 1" when you play Koichi; Second, we can digivolve Koichi into LV4 purple hybrid digimon to do another attack or "retaliation" 1 of opponent rested digimon.