I don't reckon they'd be that daft, it's not like they'd be bringing in a seasoned pro to fill the gap because it'd be the same for Blackwell. Though they could replace Gilo with just Udal.
I'm counting on Panesar being in the first Test side along with Udal. So in short (as the above makes no sense

), single spinner = Udal (help....) and if they go with two spinners then it has to be Udal and Panesar.
I think picking two spinners should be employed just to save Freddie's career, I'm really really worried that he's getting flogged by the captain way way too much. Not only is his batting being affected but he's going to get properly crocked soon if this carries on even though he's a superhero. The two spinners may be able to take some of the overs from him even if they aren't used as strike bowlers all the time.