How about tossing the Warehouse 13 version of H.G. Wells into the series.

Just switching things up so it is Jaime Murray as H.G. Wells could lend some zing to the interactions.

In Warehouse 13 her brother was her front for writing and being a Warehouse agent she had interesting stuff. So I can see having both H G Wells around. Her showing up and asking her brother just what have you been doing with my time machine would be amusing.

Imagine the confusion that would start!

The big problem with that, of course, is that Warehouse 13 Wells has VERY good reasons to want to change history - if she had a time machine that could actually change anything (Warehouse 13 has time travel of a sort, which she invented, but you can't alter history, not even small details) she'd use it herself, and if she succeeded she'd erase all her reasons for involvement in events in the 21st century.

That doesn't rule out her appearance, of course, but the character and her motives would be very different to what we see in Warehouse 13.

Further to this, Warehouse 13 Wells is apparently going to be back in a couple of weeks, according to the announcement at the end of this week's episode.