From what I have seen so far.

Injuries if players push too hard too soon. (cant afford to lose some of our key players)
No crowd, doesn't seem to affect the play at all (In our case though not having fans on your back if we don't play too well is an advantage to us at home)
5 subs is a great idea, and one I think Slav will love. (Any chance that could be a change for the future? would keep a lot more players involved)