Overall, I think this is your best fan-made unit to date. But I feel that some changes could be made to make it even more realistic. Starting with...

Stats - Most units with 47 cost have total stats of 16320 or somewhere very close to it. Also, the highest Def of any current unit is Hisui, with 3052 Def, so I think Ishrin's Def may be a little high. - Something like 7978/2783/3026/2534 would be good. - Might as well keep the imp distribution to 1250/400/800/600

BB/SBB - You could bump up the Atk/Def down on BB from 40% to 50%, and increase the ailment proc chance to the standard 75% - And decrease the Atk/Def down on atk on SBB from 30% to 20 or 25% since the highest non-global unit only does 25%. - No reason for the SBB modifier to deviate from the usual 580% too. - UBB modifier for OE units is at least 1500% - only Stein has less - Should also change the dmg to HP part from 40% to 75% (or even 100%)

SP - You could decrease the BC efficacy option from 30% to 10 or 15% (refer to Avant/Sirius etc.) - And include the 2 30SP options to BB as well. - Change both the 2 turn mitigation and the dmg to HP to 40SP if you want to prevent people from choosing both plus the negate stat debuffs.