The former Southend centre-back appeared as a trialist in Rangers' 1-0 defeat at Sheffield Wednesday on Wednesday night.
Mohsni's agent held talks with Rangers chief executive Craig Mather before the game and McCoist is optimistic a deal can be done to allow the player to sign for Rangers when their transfer embargo ends on September 1.
McCoist told the club's official website: "As ever, I'm very, very hopeful we can get something done. He's obviously a good player for us and came on in the second half to look solid and sound.
"I think the finances have led to a little bit of a stumbling block and I don't take much to do with that.
"All I know is the player wants to come, we certainly want the player and when two parties want the same thing you've always got a chance."
As McCoist plans to field some of his summer signings as trialists in competitive fixtures before the club can officially register them, Mohsni might not be able to feature until September.
McCoist, whose team kick off their season against Albion Rovers in a Ramsdens Cup tie at Livingston on Sunday, said: "It's far from ideal that we've a situation where certain players can only play in certain games and some can't play at all.
"I don't think we can play the trialists unless their registrations were in Scotland at their last clubs but I'm not sure on that.
"Whatever the situation, we've trained really, really hard and we've had a good level of opposition in our pre-season games.
"I think we are ready for the big kick-off on Sunday and we're really looking forward to getting our season under way."
- Sports & Recreation