Looks good but in typical Cisco form it ain't cheap
A Government organisation I am working with was looking at this very scenario recently with the same hardware and software. One of the biggest hurdles was the cost - we were considering ISR1100's for the smaller offices since we didn't need anything more. All looked good till we saw the SDWAN 100M license for these units - it was 5x the price of the chassis! Suddenly our small offices were going to cost $3k per user to connect up.
The license cost for the head end ASR1k is equally mindbending ;-)