The trend of gbp/jpy has been a slow trend upward, with waves that are structured. The movements in GBP/JPY dictate the movements.
The options are to await the minimal stage at the wave cycle of GBP/JPY to go into trades long in GBP/USD and USD/JPY, effectively taking USD out of the film.
If your bullish on GBP/JPY
1) long gbp/jpy outright
2) long equal usd amounts of GBP/USD and USD/JPY