It could bring stability and decentralize the network, at least initially, depending on the algo. But preventing 51% attack has nothing to do with the algo. The algo has to do with decentralization and can be more or less ASIC resistant. But in the end, if enough money is involved (like in Bitcoin mining), every algorithm can be ASIC-ed. There are even attempts to incorporate as many as 16 different algorithms into one protocol, as RavenCoin did in its
X16c algo:
The X16R hashing algorithm consists of 16 hashing algorithms operating in chain fashion with the ordering dependent on the last 8 bytes (16 nibbles) of the hash of the previous block.
The algorithms are as follows:
0=blake
1=bmw
2=groestl
3=jh
4=keccak
5=skein
6=luffa
7=cubehash
8=shavite
9=simd
A=echo
B=hamsi
C=fugue
D=shabal
E=whirlpool
F=sha512
Source:
https://ravencoin.org/wp-content/uploads/2018/01/X16R-Whitepaper-3.pdf