I don't think people understand how much a Harbaugh team relies on a strong O-line. It's absolutely been the key to the team's success.
How are you going to replace an all-pro' level LG? New 1000-yard receivers pop up much more often than all-pro' guards.
I'll take a potential pro bowl WR over an All-Pro LG any day of the week and twice on Sunday. Look at the difference in this offense with Crabtree in the lineup compared to when he was not, look at how much its helped Kaepernick. Did Iupati's absence make that same type of difference? No it didn't.
That being said, I'm hoping we can sign both of them along with Aldon this offseason. We WILL have ample cap space to do so as we are in excellent cap position for the foreseeable future if I remember correctly.