You can totally do as you describe with the RIMS and NG. Just make sure to get some type of shielding for your connections so the boil doesn't melt them!
But also, here's my 2 pennies on where you're at. At some point you will have assimilated as much info as is feasible, and then you'll just need to make the best decision you can and pull the trigger. Identify your priorities as you're noodling on what you want and use those to guide your decision. Chances are you will not get your perfect, ideal system out of the gate. Most of us find tweaks and changes, even for the off-the-shelf systems, so that they're better suited for our needs.
My driving priority at the onset was to make good beer for the least amount of money and effort. That's why I was a no-chill stove top brewer for a while. However, things morph and evolve and this priority changed over time. Now I would say my priority is to make the BEST beer, but still for the least amount of money and effort.
I'll end this rambling with a pitch for the guy I got my system from. Steven @Brausupply. Right now he's running a big 20% off sale (use coupon code BlackFriday2016). You can get a complete eBIAB system for $739 x 0.8 = $591. No need to spend $1000-$1500. Link is below.
https://brausupply.com/collections/...oss-automated-brew-system?variant=19286933701
Believe me, I'm noticing the troubles with selecting the right system and to make matters worse my OCD side also interferes with my decisions. I don't think that I'll stay a BIAB brewer, as I really would like to have the ability for step mashes, and testing the differences between sparge techniques - not that I think that even really matters. At the moment, honestly, I'm thinking about doing a 2-vessel System.
I figure having a dedicated Mash Tun would give me the ability to do Mashes without the worry of a bag, or buy an expensive SS basket, and I'd still be re-circulating with full mash volume. I would use the kettle to increase temperature manually, until I can afford a Tower of Power to ignite my burner and maintain temperatures automatically. While I truly like the idea of BIAB, I'm not a huge fan of the bag itself being in contact with heat to perform a step mash. (Call me crazy, because it is very likely that I am, but I feel stainless is more "sterile." That could also just be in my head, and I don't mean to take any credit away from BIAB methods because I do plan to start that way. It's just a personal preference.)
This preference along with the OCD need to have matching kettles makes the decision difficult because choosing the right kettle, which would be able to grow into the complete system I have dreamed in my head, is difficult for me. I get stuck between cost, appearance, quality, upgrade-ability. The Spike Kettles are likely in the winning for me, but (and this is really stupid, but once again an example of my OCD nature) I'd like to have my re-circulation valve on the side of the kettle with an elbow to fit the valve for the aesthetics. This has led me down a path of considering the G2 BoilerMaker instead, however, those would increase the overall cost as they are more expensive. The expense increase then led me to Ss Brewtech, but once again the standard re-circ port messes with my OCD nature and I would likely be annoyed looking at it (I know, it is a stupid reason), and finally I've considered Anvil as the price is lower than the others, but I'm not fund of their false bottom. It just seems to have a large amount of space wasted underneath being it sits above the drain tube. I'm sure this would not make much of a difference once I purchase my pump and begin doing 60-min re-circulating mashes, but until I get to that stage what effects would the extra space inherently add? All of this is hindered by the lack of reviews and videos to see these items in action as I would use them. This forum, and my post, along with a few on reddit, have been a way for me to ask questions in hopes that perhaps someone would make the decision for me to a certain degree.
I'm possibly simply suffering from information overload...
When I started brewing 5-6 years ago I was completely content with my 5gal coolers and 8 gallon basic pot, but now that I have a new home and after taking a year hiatus from brewing I realize it is really time to step up my game in order to brew some award quality brews.
EDIT: and to go with all that long text: I'm pretty certain that if I were to find a place that made custom SS baskets with sanitary welds and a professionally flawless appearance I'd likely stick just to BIAB...