I think the danger there would be that people see it as just that, the Lib Dems with a new name, when the new lot have been trying to distance themselves from the "old, failed parties". It's a conundrum for them, as it would be very tough to make any sort of impact in an election (in terms of winning seats themselves, rather than acting as a spoiler) without at least an electoral pact with the LDs.
It says a lot for the toughness of what they're doing that the SDP-Libs was actually a successful example of a third party emerging in the UK (edit - should really say England, as the SNP have also clearly done it since), it being the first time since the 20s that a third party had achieved more than 20% and won over 20 seats.