I did some comparrison of characteristics of some of the power transistors listed. I do not feel that the ECG153 is really a better replacement for the 2SA1357. The ECG153 gets it's higher power rating from higher voltage ratings, not higher current ratings.
The voltage is not going to change significantly (same batt) without frying both the recvr board and the driver board.
The desire here, as I interpret it, is to run higher current, or current for a longer time without suffering heat related failure. To achieve that, I propose that you considet the NTE common characteristic replacement suggested for the 2SA1357; NTE2514. It has Higher Power dissipation rating (20W, twice) and higher max collector current rating, with other characteristics well within ball-park of the 2SA1357. Just MHO and I assume no responsibility for anyone foolish enough to follow it.

Characteristic Symbol NTE2514 2SA1357 BD178 BD436 NTE153 ECG153
Collector-Base Voltage Vcbo -60V -35V -60V -32V -90V -90V
Collector-Emitter Voltage Vceo -60V -20V -60V -32V -90V -90V
Emitter-Base Voltage Vebo -6V -8V -5V -5V -5V -5V
Collector Current DC Ic DC -8A -5A -3A -4A -4A -4A
Collector Current Pulsed Ic p -12A -8A -7A -7A
Base Current Ib -1A -1A -3A -3A
Collector Power Ta=25 C P am 1.2W 1.5W
Collector Power Tc=25 C P c 20W 10W 30W 36W 40W 40W
Junction Temp Tj 150 C 150 C 150 C 150 C 150 C 150 C
Collector Cut-off Current Icbo 1uA -100uA -100uA -100uA 20uA 20uA
Emitter Cut-off Current Iebo 1uA -100uA 1mA 1mA 10uA 10uA
Collector-Emitter Breakdown Voltage V(br) ceo 50V -20V -90V -90V
DC Current Gain hFE1 max hFE1max 240 320 250 140 200 200
DC Current Gain hFE1 min hFE1min 140 100 40 30 40 40
DC Current Gain hFE2 min hFE2min 35 70 15 40 15 15
Collector-Emitter Saturation Voltage Vce(sat) 250mV -1.0V -0.8V -0.5V -1.5V -1.5V
Base-Emitter Voltage Vbe -1.3V -1.5V -1.3V -1.1V -1.5V -1.5V
Transition Frequency fT 130MHz 170MHz 3MHz 3MHz 8MHz 8MHz
Collector Output Capacitance Cob 65pF 62pF 85pF 85pF