In the standard C&CN game, the player isn't allowed to reduce their hand below 2 for squaring. Does this still apply with these solitaire rules? If so, then doesn't this limit need re-calibrating for the solitaire card allowance? The equivalent limit would, I think, be 1 card always in hand minimum and the +1d would count as a card in hand.
So for example, a player with 1 card +1d, would be able to square. Also, the +1d would be "lost" first, before definite card draws, maybe ?
Another thought; for the the base game you might make it less likely that First Strike will be played if that side has units in square.