We have to assume that the 2-way peg is unbreakable. Same as bitcoin blockchain is unbreakable.
spvp is new type of group signature (it can replace ECDSA M-of-N multi-signature)
Quote
Bitcoins blockheaders can be regarded as an example of a dynamic-membership multi-party signature
(or DMMS), which we consider to be of independent interest as a new type of group signature.
(or DMMS), which we consider to be of independent interest as a new type of group signature.
spvp is new type of group signature (it can replace ECDSA M-of-N multi-signature)
spvp is vaporware and will likely be much less secure than MM.
[/quote]
They're two totally different things and both work in tandem. What you just said makes no sense
SPVP is absolutely not vaporware. It might not be ready to implement as we are speaking but there are real maths behind it.