It's OK to replicate some mechanics from other games. I am doing it myself for my starcraft clone, but in the end I want a game that can stand on it's own.
Besides streamlining the game mechanics, the solo playability is what will make this game stand out from the original even if we can clearly see the original source of inspiration.
Look at Forbidden Star for additional idea since this game is also a derivation of Star Craft BG. It will give you a good example of what they kept and what they left out while trying to find why.
I put additional thoughts on the card design. In a nutshell, the numeric stats(MTG style) would remain on the units token while cards would have an RPS value. Winning the RPS makes you attack first (winning ties). But also some abilities could trigger only if you win the RPS. Each card would have potential abilities that could trigger if you have the matching tech, pair of units, etc.
The good thing is that I found a way around this wall that I hit many months ago even if all the elements to find the solution were known. Game design inspiration is so unpredictable.
