Cards and Number of Copies
For Digitama, I will only use 4 copies of Demiveemon because we will use only 4 copies of Veemon as for LV3 digimon. Tamer Takumi Aiba gives draw power and to avoid opponent rushing by attacking using their LV3 digimon, so I will use 4 copies.
Other than those digimon I wrote in the post for this strategy, I would like to use the Omnimon from BT5 (3 copies) to take benefit of Shingeki (Blitz) to attack when it evolves. Since our strategy is to build more LV6 under its digivolution source, this Omnimon can take advantage of this build and stay longer in the battle.
Other combo for the deck
The LV3 Shoutmon is used to reveal cards and take to hand 1 digimon with [Shoutmon] in its name and 1 digimon with Blitz, this will help shorting the hands and deck. If we able to build the digivolution base for ShoutmonDX or ZekeGreymon that includes Shoutmon and OmniShoutmon, it adds 2000DP and SecurityAttack+1. We can do attacking security first then digivolve to LV7 BT5 Omnimon, unsuspend this Omnimon and do another attack (this is considered as another plan incase we cannot draw BT1 Omnimon at this turn). Up till this point, it already checked 4 securities.
The LV5 Vermilimon – 5 cost to play, to use in case we cannot draw low cost LV6, and 3 copies of Phoenixmon (10 cost to play and 2 cost to digivolve). I also use 2 copies of white Tamer Tai Kamiya&Matt Ishida to gain 2 memory when opponent has LV6 digimon or higher. Since we are giving opponent a alots of memory, there is high chance that they will move up to LV6 or LV7.
By the first look, you might think this deck dont prepare "defense" strategy. Actually, with the Takumi Aiba and Shoutmon DX, I really dont worry if opponent does rushing. Draw power are also supported by blue LV3 Veemon and Takumi Aiba, the LV3 Shoutmon gives more support to get "blitz" cards (ZekeGreymon, Shoutmon DX and BT5 Omnimon). We can get more memory from red option card Gravity Crush and white tamer Tai&Matt.