Hello,
I dont think there is any problem segregating your Internet and the MPLS connections on two different routers. The only thing i would recommend is to ensure that the routing within your environment i.e. Intra-Domain so that traffic leaves the correct router.
Another thing that I would like to understand is what is the purpose of having 4 ISP connections for Internet. Are they sharing the Internet Routing table. Even too much redundancy is not really good in the network
Regards
Vinit
Thanks
--Vinit