This is my guess for where a loop would go west of SH-6:

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I'm skeptical the part southeast of 60 (Raymond Stotzer Pky/the airport) will be the route. Would probably require taking 15-20+ large lot houses (wealthy) and the relocation of a bunch of mobile homes. Could be politically tough on the local level.
In the latest Google Earth (6/23) view for that area, it looks like 2818 (Harvey Mitchell Pky) is being widened into feeder roads with room for freeway lanes and overpasses from Stotzer Pky to Wellborn (the RR tracks). That is more likely to be the route, as it gets very close to aTm. East of Wellborn is also a wide ROW of 300'+ and note the large radius curve setback going east from Harvey Mitchell to south on Texas Ave. The short stretch of Texas Ave needed conversion to freeway would require perhaps 2 houses and a half dozen businesses. Seems like a more cost effective alternative that might serve the most users. I'd guess any east side loop is likely to tie in south of there on Hwy 6, so the existing interchange of Hwy 6 to/from Texas Ave wouldn't require much modification.
An alternative would be to route from Harvey Mitchell southeast along Wellborn to William D. Finch Pky. Expensive, would require taking at least 8 apartment buildings, several condos, and several businesses on the south side of the RR tracks (plus anything that springs up on the vacant land in the next decade). Depending on design they might also move the RR west some and build on the east side of the tracks. More $$$. Or elevate for 2 miles over Wellborn, but probably cost prohibitive and politically toxic given all the neighborhoods close to Wellborn.
There has been talk over many years of relocating the RR to a bypass of BCS, but it never went far because of the huge cost and removal would still not provide enough ROW along Wellborn for a freeway without taking those apartments and businesses. I would guess a Wellborn option would be more expensive than your route, but perhaps more politically doable.
The proposed routes west of the Brazos are way out there (for BCS) and through high quality farm areas (much of it floodplain). There was plenty of outcry when similar land was acquired for the railroad yard further north near Hearne. The railroads have sizeable powers of eminent domain and are less beholden to local politics (though still a factor) so that option may be tough for the MPO, or resulting in years more of decision delays.
I'd guess the Stotzer Pky to Harvey Mitchell Pky to Texas Ave option will end up being the route built.
BTW, it's hard to foresee much demand or economic justification for I-14 east of Hwy 6. The Sam Houston National Forest is a huge swath that provides a northern boundary for the eventual dense suburban type development of the Houston area. It will be a long, long time before there is much north of it on the Huntsville side. Better use of limited dollars to upgrade 105 from Navasota/aggy tollway to I-45 in Conroe.