As one of our regular posters said though, from a flap 40 approach Vref 40 + 20 represents the minimum speed for a one engine go around (V2 flap 1). So is there an objection to selecting flap 15 initially followed rapidly by flap 1 ?
My 2c here only so don't take it as authoritative but I'd think the point of accelerating to Vref40+20 initially is to place you at F15 minimum manoeuvre speed for a OEI approach which allows you the full manoeuvre margin (because you may have had landing flap selected on base leg due to strong tailwinds on base near circuit height say and you may need to use the full 25* AoB to roll onto final). If you drift through the centreline for example and execute a missed approach you're starting from a familiar point so I'd guess "go around flaps 1" would be what's required as per OEI GA. However assuming you don't have a bug for Vref15 displayed, and in keeping with what you said re V2 F1, then you're in no place to assume you're above V2+15/Vref+15 and so I'd manoeuvre with care up to 15* AoB, you've just taken the LE slats in 1 stage after all. Once the initial turn is out the way then I suppose you could accelerate and clean up the last stage of flap. More than happy to be corrected if anyone knows otherwise however.