Putting it all together - from the most simplistic to the most flexible.
If you're going to use just one single-width instrument at a time, it's entirely possible to do this with a TM501 (single width) power module then swap counter or DMM in as required. Do so with the power off, please. Otherwise, get hold of a TM502 or larger power module with which to run your accessories.
General-use:
DM-501A, DM-502A, DM-504A or DM-511 plus DC-503A, DC-504A or DC-505A
Communications service work:
DM-501A, DM-504A or DM-511 plus DC-501, DC-505A, DC-510 (with DP-501 Prescaler or an R-Y-O equivalent) or a DC-508/A.
Engineering and calibration lab work (requires TM5006 power module):
DC-5010, DP-501 Prescaler and DM-5120 DMM.
The combination listed immediately above can fetch north of $1200 if you're not a prudent shopper and south of $500 if you are. Make them an offer they won't refuse. I got all three modules for $450, albeit via separate sales.