After some thought this sounds like a workable idea.
I went on the Morebeer site and came up with these cost estimates:
Prices are rounded off:
1 55 gallon Blichmann Kettle with
2 Boil Coils $1100
1 55 Gallon Ketttle for mash tun $675
2 Rims Rocket 240v $480
2 TOP control units $1150
55 Gallon false bottom $199
(I might use brewing basket similar to Colorado Brewing Systems)
2 High temperature pumps $400
Not included is a table/stand to put everything on, hoses, connectors, and if using a mesh basket, a hoist to lift the spent grain.
Total of what is listed above: $4004
The Colarado Brewing System Nano Brewer Dual is $5300
but comes with a hoist arrangement and a plate chiller.
Their system should be a little faster since pumping from the mash kettle to the brew kettle isn't required.
Since you already have one RIMS rocket and a controller you can take about $850 off the above price?
There are some pros/cons to using a RIMS in this kind of arrangement.
Sabco has a 1bbl, 3 kettle, gas fired with electric RIMS for $16K+.
Lots to think about, my 2 cents is a system that has been tested and refined is worth a little more money.
You can probably build something like the CBS with components you find on your own for a little less.