Hi there, msfujino
I would too, Allot is only accessible from SDK ESP IDF so it seems, all the extra GATT stuff isn’t in the BLE arduino LIB’s and idunno how much is in the softdevice too?
Nordic has 8 concurrent connections of peripherals to one central Blinky example with dev board kit, (would be a very attractive SEEED demo btw) and Up to 20 in a round robin state machine method. and to get full transmit power +8dbm I don’t think its truely supported even in adafruit , because of the coded PHY stuff? (above my level) they use Zephyr RTOS lower level.
I hope someone in the engineering dept. could speak on some of this and comment on any support.
I play the powerball too so. 
GL 
PJ