Keeper Simonsen and former Everton youngster Kelly have been training with the Light Blues in recent days as McCoist looks to bolster his ranks once again.
A deal for defender Boris Pandza is still being worked on but it is another striker that the Gers boss has set his sights on first. He is keen to send keeper Scott Gallacher out on loan to get first-team action and has been pleased with how his latest two potential captures have shaped up.
McCoist said: "Both have shown up really well. Steve we're really happy with, but the problem we've got is the timing of trying to get Gall out on loan to try and play.
"We still believe it will be beneficial to the club and Gall to get out to play on a regular basis.
"He's been fantastic this season so far, but, with the greatest of respect, we've signed Cammy Bell so he will play.
"We're of the opinion that it would be beneficial to Gall and the team to get him out and in doing that we'll have to get another one in.
"It's getting the timing right. If we play Nicky Law and Jon Daly again, for example, tonight, it means they can't play the following week against East Fife, so you've got an option of playing Cammy and Nicky Clark then.
"So you could maybe get Gall out after the Berwick game (on Tuesday). The logistics are difficult but we need to keep Gall until at least Tuesday night.
"Firstly, we need to find out if there's a club willing to take him on loan.
"Sam's shown up really well. He's trained really comfortably. He's a good passer of the ball - a very intelligent footballer. We'll get a wee chat with him tomorrow."
"I still have to have a chat about who I can still then bring in, but a centre-forward would be my priority."