Loops are wonderful

This in GTweak:

if "%mch%"=="A:" (
 if not "%IsAlreadyA%"=="1" (
  set/a final+=1
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyA=1
  exit/b0
 )
)

if "%mch%"=="B:" (
 if not "%IsAlreadyB%"=="1" (
  set/a final+=2
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyB=1
  exit/b0
 )
)

if "%mch%"=="C:" (
 if not "%IsAlreadyC%"=="1" (
  set/a final+=4
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyC=1
  exit/b0
 )
)

if "%mch%"=="D:" (
 if not "%IsAlreadyD%"=="1" (
  set/a final+=8
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyD=1
  exit/b0
 )
)

if "%mch%"=="E:" (
 if not "%IsAlreadyE%"=="1" (
  set/a final+=16
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyE=1
  exit/b0
 )
)

if "%mch%"=="F:" (
 if not "%IsAlreadyF%"=="1" (
  set/a final+=32
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyF=1
  exit/b0
 )
)

if "%mch%"=="G:" (
 if not "%IsAlreadyG%"=="1" (
  set/a final+=64
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyG=1
  exit/b0
 )
)

if "%mch%"=="H:" (
 if not "%IsAlreadyH%"=="1" (
  set/a final+=128
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyH=1
  exit/b0
 )
)

if "%mch%"=="I:" (
 if not "%IsAlreadyI%"=="1" (
  set/a final+=256
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyI=1
  exit/b0
 )
)

if "%mch%"=="J:" (
 if not "%IsAlreadyJ%"=="1" (
  set/a final+=512
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyJ=1
  exit/b0
 )
)

if "%mch%"=="K:" (
 if not "%IsAlreadyK%"=="1" (
  set/a final+=1024
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyK=1
  exit/b0
 )
)

if "%mch%"=="L:" (
 if not "%IsAlreadyL%"=="1" (
  set/a final+=2048
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyL=1
  exit/b0
 )
)

if "%mch%"=="M:" (
 if not "%IsAlreadyM%"=="1" (
  set/a final+=4096
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyM=1
  exit/b0
 )
)

if "%mch%"=="N:" (
 if not "%IsAlreadyN%"=="1" (
  set/a final+=8192
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyN=1
  exit/b0
 )
)

if "%mch%"=="O:" (
 if not "%IsAlreadyO%"=="1" (
  set/a final+=16384
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyO=1
  exit/b0
 )
)

if "%mch%"=="P:" (
 if not "%IsAlreadyP%"=="1" (
  set/a final+=32768
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyP=1
  exit/b0
 )
)

if "%mch%"=="Q:" (
 if not "%IsAlreadyQ%"=="1" (
  set/a final+=65536
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyQ=1
  exit/b0
 )
)

if "%mch%"=="R:" (
 if not "%IsAlreadyR%"=="1" (
  set/a final+=131072
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyR=1
  exit/b0
 )
)

if "%mch%"=="S:" (
 if not "%IsAlreadyS%"=="1" (
  set/a final+=262144
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyS=1
  exit/b0
 )
)

if "%mch%"=="T:" (
 if not "%IsAlreadyT%"=="1" (
  set/a final+=524288
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyT=1
  exit/b0
 )
)

if "%mch%"=="U:" (
 if not "%IsAlreadyU%"=="1" (
  set/a final+=1048576
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyU=1
  exit/b0
 )
)

if "%mch%"=="V:" (
 if not "%IsAlreadyV%"=="1" (
  set/a final+=2097152
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyV=1
  exit/b0
 )
)

if "%mch%"=="W:" (
 if not "%IsAlreadyW%"=="1" (
  set/a final+=4194304
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyW=1
  exit/b0
 )
)

if "%mch%"=="X:" (
 if not "%IsAlreadyX%"=="1" (
  set/a final+=8388608
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyX=1
  exit/b0
 )
)

if "%mch%"=="Y:" (
 if not "%IsAlreadyY%"=="1" (
  set/a final+=16777216
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyY=1
  exit/b0
 )
)

if "%mch%"=="Z:" (
 if not "%IsAlreadyZ%"=="1" (
  set/a final+=33554432
  echo.
  echo  The '%mch%' drive added
  set IsAlreadyZ=1
  exit/b0
 )
)

will be replaced by this:

:GenerateDrivePolicyValue
set alphabet=A;B;C;D;E;F;G;H;I;J;K;L;M;N;O;P;Q;R;S;T;U;V;W;X;Y;Z
set init=1
for %%A in (%alphabet%) do (call:LoadArrayProc %%A)
set init=
for %%A in (%*) do (for %%B in (%alphabet%) do (if "%%A"=="%%B:" (call:RaiseValBy %%B||echo  Drive '%%B:' has already been added)))
for %%A in (%alphabet%) do (set Drive%%A=&if defined IsAlready%%A (set IsAlready%%A=))
set alphabet=
call:ThrowErrorLevel %final%
exit/b%errorlevel%
:ThrowErrorLevel
set final=
exit/b%1
:LoadArrayProc
set Drive%1=%init%&set/a init*=2&exit/b0
:RaiseValBy
set var1=%% IsAlready%1 %%
set var1=%var1: =%
for %%A in (%var1%) do (call:RaiseValBy_1 %%A||exit/b1)
set var2=%% Drive%1 %%
set var2=%var2: =%
call set/a final=%final%+%var2%
set IsAlready%1=1
set var2=&set var1=
exit/b0
:RaiseValBy_1
if "%1"=="1" (exit/b1) else (exit/b0)

Above code returns desired NoDrives/NoViewOnDrive/NoDriveAutoRun policy value in ERRORLEVEL, so that you can use it as a function in your scripts:

call:GenerateDrivePolicyValue E: I: L: O: P: R: V:
reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\policies\Explorer" /v "NoDrives" /t "REG_DWORD" /d "%errorlevel%" /f>nul 2>&1

Here is the result:



Please note that ERRORLEVEL will get overwritten after REG execution, so you need to save it to another variable:

set PolicyValue=%errorlevel%

... or call value generation routine multiple times.