Internal bgp and upstream gateway

[yctn]

so i have a /22 network. my ISP provides me with a default gateway.
so i can configure ip's on boxes/vm's and they are reachable from the internet.

i wish to run bgp internal cause i desire to run an application that run exclusively on BGP.
so my idea was as following.
configure bgp to use /27.
so i picked a segment within my public ip range. that i wanne use with bgp.
and configured the following.

--ISP GW <--> pfsense <--> bgp to nodes.

which means(i think) that pfsense need to accounce ARP on my switch so the default gateway knows tha traffic for ip X should be send to pfsense which internly will send it on over bgp to nodes.

the pfsense has 2 interfaces a WAN and a LAN.

would this be doable?/is this making any sense at all.