Trying to chainload iPXE with full feature set from a lesser featured one, whilst still being able to boot non-supported cards with UNDI

dhcpd.conf

ddns-update-style none;
deny bootp; #default
authoritative;

include "/etc/dhcp/ipxe-option-space.conf";

# GREEN (private network)
subnet 10.1.1.0 netmask 255.255.255.0 {
    range 10.1.1.100 10.1.1.199;
    option subnet-mask 255.255.255.0;
    option routers 10.1.1.1;                        # firewall.smidsrod.lan

    default-lease-time 3600;
    max-lease-time 86400;

    option domain-name "smidsrod.lan";
    option domain-search "smidsrod.lan";
    option domain-name-servers 10.1.1.1;            # firewall.smidsrod.lan

    option ntp-servers 132.163.97.3,132.163.97.2;   # time.nist.gov
    option log-servers 10.1.1.2;                    # core.smidsrod.lan
    option lpr-servers 10.1.1.8;                    # laserjet.smidsrod.lan

    include "/etc/dhcp/ipxe-green.conf";
}

use-host-decl-names on;

include "/etc/dhcp/static.conf";

ipxe-green.conf

# For information on valid values for option arch, see these links:
# https://git.ipxe.org/ipxe.git/commitdiff/af9afd0a86aeac1eed28b5028c3de669515fc7fc
# https://git.ipxe.org/ipxe.git/blob/HEAD:/src/include/ipxe/dhcp.h#l275
# https://www.rfc-editor.org/errata_search.php?rfc=4578
#
# I like to use native iPXE drivers (they're faster and more stable), so
# give ipxe.pxe/ipxe.efi to all non-iPXE clients, use undionly.kpxe/snponly.efi
# only if you have unsupported or misbehaving NICs.

allow bootp;
allow booting;
next-server 10.1.1.2; # core.smidsrod.lan

# Disable ProxyDHCP, we're in control of the primary DHCP server
option ipxe.no-pxedhcp 1;

# Make sure the iPXE we're loading supports the features we need, if not
# load a full-featured version.  See ipxe-option-space.conf for definitions.
if    exists ipxe.http
  and exists ipxe.menu
  and exists ipxe.nfs           # NB: not enabled in iPXE by default
  and (
        ( exists ipxe.pxe
      and exists ipxe.bzimage
      and exists ipxe.elf
      and exists ipxe.comboot   # NB: not enabled in iPXE by default
      and exists ipxe.iscsi
        ) or (
          exists ipxe.efi
        )
      ) {
    filename "nfs://nas.smidsrod.lan/raid/boot/boot.ipxe";
    #filename "http://boot.smidsrod.lan/boot.ipxe";
} elsif option arch = 00:09 { # EFI BC
} elsif option arch = 00:08 { # EFI Xscale
} elsif option arch = 00:07 {
    # EFI x86-64 (Intel x86 64-bit EFI mode)
    # - most commonly used on newer hardware
    filename "ipxe-x64.efi";
    #filename "snponly-x64.efi";
} elsif option arch = 00:06 {
    # EFI IA32 (Intel x86 32-bit EFI mode)
    # - almost never seen in the wild
    filename "ipxe-x86.efi";
    #filename "snponly-x86.efi";
} elsif option arch = 00:05 { # Intel Lean Client
} elsif option arch = 00:04 { # Arc x86
} elsif option arch = 00:03 { # DEC Alpha
} elsif option arch = 00:02 { # EFI Itanium
} elsif option arch = 00:01 { # NEC/PC98
} else {
    # Intel x86PC (Intel x86 32-bit legacy BIOS mode)
    # - technically option arch = 00:00, but we use it as fallback
    filename "ipxe.pxe";
    #filename "undionly.kpxe";
}

ipxe-option-space.conf

# Declare the iPXE/gPXE/Etherboot option space
option space ipxe;
option ipxe-encap-opts code 175 = encapsulate ipxe;

# iPXE options, can be set in DHCP response packet
option ipxe.priority         code   1 = signed integer 8;
option ipxe.keep-san         code   8 = unsigned integer 8;
option ipxe.skip-san-boot    code   9 = unsigned integer 8;
option ipxe.syslogs          code  85 = string;
option ipxe.cert             code  91 = string;
option ipxe.privkey          code  92 = string;
option ipxe.crosscert        code  93 = string;
option ipxe.no-pxedhcp       code 176 = unsigned integer 8;
option ipxe.bus-id           code 177 = string;
option ipxe.san-filename     code 188 = string;
option ipxe.bios-drive       code 189 = unsigned integer 8;
option ipxe.username         code 190 = string;
option ipxe.password         code 191 = string;
option ipxe.reverse-username code 192 = string;
option ipxe.reverse-password code 193 = string;
option ipxe.version          code 235 = string;
option iscsi-initiator-iqn   code 203 = string;

# iPXE feature flags, set in DHCP request packet
option ipxe.pxeext    code 16 = unsigned integer 8;
option ipxe.iscsi     code 17 = unsigned integer 8;
option ipxe.aoe       code 18 = unsigned integer 8;
option ipxe.http      code 19 = unsigned integer 8;
option ipxe.https     code 20 = unsigned integer 8;
option ipxe.tftp      code 21 = unsigned integer 8;
option ipxe.ftp       code 22 = unsigned integer 8;
option ipxe.dns       code 23 = unsigned integer 8;
option ipxe.bzimage   code 24 = unsigned integer 8;
option ipxe.multiboot code 25 = unsigned integer 8;
option ipxe.slam      code 26 = unsigned integer 8;
option ipxe.srp       code 27 = unsigned integer 8;
option ipxe.nbi       code 32 = unsigned integer 8;
option ipxe.pxe       code 33 = unsigned integer 8;
option ipxe.elf       code 34 = unsigned integer 8;
option ipxe.comboot   code 35 = unsigned integer 8;
option ipxe.efi       code 36 = unsigned integer 8;
option ipxe.fcoe      code 37 = unsigned integer 8;
option ipxe.vlan      code 38 = unsigned integer 8;
option ipxe.menu      code 39 = unsigned integer 8;
option ipxe.sdi       code 40 = unsigned integer 8;
option ipxe.nfs       code 41 = unsigned integer 8;

# Other useful general options
# http://www.ietf.org/assignments/dhcpv6-parameters/dhcpv6-parameters.txt
option arch code 93 = unsigned integer 16;