Would you gamble on Malkin and Hornqvist meshing together with Pearson as the LW? They could always go back to that line. If you're content with putting a $3.5 million guy on the 4th line for this year, you could have Pearson-Malkin-Hornqvist, ZAR-Brassard-Kessel and Grant-Cullen-Rust as your 2nd-4th lines. I just don't like that 2nd line at all and I don't think they'll put Rust on the 4th line long term, I think they'd sooner trade him.
Gamble on in terms of giving it a few games? Sure, depending on what else is going and how much I fancy seeing McHurt rage that day. Actually expect it to work? Eh... I'm 50-50 on that. I'm a lot higher on Pearson-Malkin-Rust working, that heavily resembles some successful lines of the past and if Rust would hit a hot streak I think it would be an awesome line.
If Rust slips to the 4th... I think he's got until the end of the season, barring a good trade, before he's gone.
Although I'm more curious about a scenario where Simon and Rust stick as the top 6 wingers for the season. Like, how long do you look at 12m of winger in the bottom 6 before going "Okay, this is silly?"
p.s. Re Sprong - I think his main problem is his hockey IQ + experience levels simply don't add up to being in a good place and doing good things often enough.