As for gold, I could see the argument that gold itself is already hyper-volatile and that no tweak is necessary,
What about 50/50 mix of a 2X daily gold fund and a gold mining shares fund for "volatile gold"? How much more volatile is gold (as measured by SD) than the other two assets?
but what about stocks? Maybe a small-cap-cap value fund? That gives you a bit more volatility, but breaks the sector neutrality of a total stock index.
Man, what a crazy PP you would have with EDV, VBR, and GLD.
Could anyone really have stomached holding this PP from 1996 to 1999? Using DFSVX for small value (I don't think VBR existed back then), and BTTRX (with BTTTX for 1996 since BTTRX only started in February of that year) for zeros, I get the following returns for those years for a 33/33/33 mix of SV, gold, and zeroes
1996 = 2.97%
1997 = 13.05%
1998 = 4.43%
1999 = -2.42%
The zeroes smacked you in 1996 and 1999; the gold hurt you big time in 1997, and the SV killed you in 1998....all of this when the broad market as a whole was giving 20%+ returns each year (and let's not even get into what large growth or the NASDAQ were doing). You actually woud have LOST money in 1999. Honestly, I think you'd have done better these four years in CDs or t-bills. The PP's greatest weakness is people quitting it due to underperformance during bull markets and this "improved" version would have been even more vulnerable than usual to such tracking error.
I would suggest replacing half of the SV with either a NASDAQ-100 fund (or even a 2X NASDAQ-100 fund) or with a high beta ETF. Either one of those would have done far better during the mid to late 90s bull market (and in 2003-07, and 2009-10) than a PP with just SV for its stock allocation.