It depends how greedy you are. Gayle's a decent opener, but he's not great or even excellent.
The benchmark for ODI batting nowadays are guys like Kohli, AMla, Sanga, ABDV and Joe Root. In the 90s, which had the toughest ODI bowling attacks, it was guys like Tendy, Lara and Anwar. In the 80s, Greenidge, Viv, Chappell. Gayle's well below all those groups.
In ODIs, opening is the easiest position and Gayle is in the easiest era of ODI batting rules, pitches and opponents. Yet he only averages 37, or 34 as an opener when you omit Zimbabwe, Canada, Netherlands, Scotland and Bangladesh. With his skills, he should be averaging in the high or mid 40s. If you're greedy, he should be averaging in the 50s like Amla.
Gayle's arguably WI's second, third or fourth best ODI opener (Greenidge, Haynes, Lara and Chanders are the only other names in contention- I'd personally only put Greenidge and Lara ahead of him, both of whom averaged 46 opening), but he still basically gives you 9 ducks for every decent innings. He never evolved beyond his block/slog style.
Part of this is bad management. He was dropped for some years at his peak and WI never paired him with another reliable opener.