PowerShell can do that first part for PS cmdlets rather than general man pages; Get-Command searches for available functions, loaded module exports and executables in the path. It takes a parameter -Module which limits that to things exported by just one module. You can use Get-Help to find out about just that parameter, e.g.:

    PS C:\> Get-Help -Name Get-Command -Parameter Module

    -Module <String[]>
    Specifies an array of modules. This cmdlet gets the commands that came from the specified modules or snap-ins.
    Enter the names of modules or snap-ins, or enter snap-in or module objects.

    This parameter takes string values, but the value of this parameter can also be a PSModuleInfo or PSSnapinInfo
    object, such as the objects that the Get-Module, Get-PSSnapin, and Import-PSSession cmdlets return.

    You can refer to this parameter by its name, Module , or by its alias, PSSnapin . The parameter name that you
    choose has no effect on the command output.

    Required?                    false
    Position?                    named
    Default value                None
    Accept pipeline input?       True (ByPropertyName)
    Accept wildcard characters?  false

Or in a shorter version, help gcm -param mod*

> I would love to have a shell that can show me (intellisense?) the most common flags and options commands are run with.

It can do some of that for PS cmdlets as well, intellisense can look into the cmdlets, find the names of exported parameters and show them all to you (not in most common order) and then for some commands you can do get-executionpolicy -Scope {tab} and it will cycle through the three available scopes. That autocomplete can be extended to do things like interrogate a database engine and complete table names, by the author, or wrapped by the user to do that. Again not really for system commands unless you wrap around them.