I do not see any problems with the bootstrap circuits. Garry has got a handle on that and posted a perfectly reasonable approach and TCM and I have discussed this area with him. This is a normal design process.
spec
Doesn't seem that way to me. Seems to be fighting to not adapt what you and tcm have been saying. Look how much it took to change from mosfets to IGBT's. Don't think it's sunk in yet that those are high side switches.