This is basically what I do. One of my bands is a 7-piece and I have the Behringer XR18 with 6 Aux sends. Each of the other band members gets their mono IEM or wedge monitor feed from one of the Aux sends, and I use the main mix for my own IEMs (cable running from MAIN R output into the back of my transmitter) - I haven't tried it in stereo yet but it's got to be done! Nothing you do to the main mix will affect the Aux mixes but any changes to channel input gains will affect everyone.
The 1U rack unit at the bottom is a Midas DN4816-O. An ethernet cable runs from the XR18's Ultranet socket to the back of the Midas, which I have set up to (mostly) output the corresponding channel immediately after the gain control - effectively an 'analog split', but done digitally. The sound guy/gal can just wire up the outputs of the Midas and do a completely independent FOH mix.
(OT: You'll see that there are holes in the XR18's rack mount ears. I made these with a step drill and fitted rubber grommets, and they are big enough to pass an XLR plug through. It took a fair bit of effort but has been well worth it for the convenience.)