Hello there,
I'll take a stab...
I assume we are talking about East US and West US here?
Pros:
1/ this will work, and I know providers who use this type of internal routing
2/ easy to set up & maintain, does not require high-end routers with fast CPU & lots of memory apart from ASBRs.
Contra:
1/ accept the inevitable upload/to-internet routing inefficiency, hopefully it will be fairly small. I.e. Your to-internet traffic could go this way:
- bottom right->up->left->West peering point->top ASBR ==>bottom ASBR ->out to internet
^^^^^^^^^^^^^^^^^^^^^^^^^^^
inefficiency here!
or
2/ accept that during a regional outage with one or several popular sites (i.e. Utah DC hosting Yourtub.com has power cut, and Yourtub.com has only 1 remaining mirror hosted by Miami DC) Your upload traffic could blackhole. To avoid this type of outage You need to either fully mesh Your ASBRs, or push full internet table down to "Enterprise"/bottom right.
3/ accept that there will be asymmetric traffic even at best of times and unless You FW are doing source NAT, You'd require state sync for Your FW. This is an endeavour in itself especially across long distances. This will be more pronounced for East-West border regions like Missouri, from where Your branch' upload traffic could exit East peering point to go to Colorado, from where return traffic will go to West peering point because it is closer to Colorado!
HTH
Thx
Alex