[Samba] NT4 with Samba4

[Sonic]

Have a need to support one NT4 server in one environment and trying to
escape
the past a bit by upgrading the PDC which currently runs Samba-3.6.24.

So far my testing has shown that Samba4-4.5 as a PDC appears to work just
fine.
I can even install Exchange 5.5 on the test NT4 server in this environment.
However attempting the same Exchange 5.5 installation when running Samba4
in AD
mode it quickly dies with this problem:
==========================================
While attempting to create the Microsoft System Attendant service, the
following error was encountered:

The account name is invalid or does not exist.

Microsoft Windows NT
ID no: 0xc0020421
==========================================

[new dialog box]
==========================================
Processing file 'D:\SERVER\SETUP\I386\server.ins', at or near line 12

The account name is invalid or does not exist.

Microsoft Windows NT
ID no: 0xc0020421
==========================================

[server.ins] around line 12
==========================================
; ServiceManager(MAD)
CreateService:MSExchangeSA;Microsoft Exchange System
Attendant;bin\mad.exe;
EventLog$OLE$NtLmSsp$RPCLOCATOR$RPCSS$LanmanWorkstation$LanmanServer$
==========================================

Basically I'd like to move the whole account into the world of AD, and the
NT4
server does appear to basically work with Samba4 as an AD up to a point (it
successfully joins the AD and users get authenticated and can logon), but
if Exchange doesn't work with it I'll be stuck in DC land for a time. The
AD users do get enumerated in the Exchange setup dialog box so I can choose
the proper service account but things go south after that - maybe akin to
how the User Manager For Domains cannot enumerate the users.

If there is a fix that would be great, if not, at least Samba has allowed
me to nurse this along much longer than would have otherwise been possible.

Thanks!