Bulk encryption with Triple Blowfish
My understanding is that the cipher's encryption:

Performs a fixed public reversible transformation of the first 128 bytes of plaintext.
Enciphers the first 8 bytes $[B_0…B_7]$ with $K_1$, $K_2$, then $K_3$
Enciphers bytes $[B_{4+8i}…B_{11+8i}]$ with $K_1$
Enciphers bytes $[B_{2+8i}…B_{9+8i}]$ with $K_2$
Enciphers bytes $[B_{1+8i}…B_{8+8i}]$ with $K_3$

The index $i\ge0$ grows as large as necessary to cover the whole plaintext (something untold takes care of the end).
Consider what happens when one enciphers the all-zero plaintext. Step 1 leaves that unchanged. Step 2 causes irregularities in the first 8 bytes. Step 3 extends that to the first 8+4=12 bytes. Step 4 extends that to the first 12+6=18 bytes.  Step 4 extends that to the first 18+7=25 bytes. But starting from byte 25 in the output of step 5, there's a key-dependent pattern that repeats every 8 bytes.
More generally, for any repeating 8-byte pattern in plaintext, there's a matching 8-byte pattern in the ciphertext (after the first 128+4+6+7=145 bytes or so).
I conclude that the proposed construction does not fully &quot;address the block size limitation in terms of bulk encryption&quot;. It does increase diffusion, thought.

I advocate against step 1. It does make the first byte of ciphertext dependent on more input bytes, but any fixed public reversible transformation of plaintext demonstrably has no cryptographic value under Chosen Plaintext Attack (as in the above), or under any Known Plaintext Attack working with random plaintext.
It's possible to make a 128-bit block cipher out of a 64-bit one. Assuming some safe operating mode like GCM, CTR, CBC, OFB, CFB on top of that, a simple such 128-bit block cipher construction that I would trust to have security up to $2^{48}$ bytes encrypted (rather than $2^{31}$ for Blowfish or $2^{64}$ for AES) uses 6 keys, assumed independent. In a Blowfish context, we could prefix a common key with 6 different 4-byte haphazard public constants. Starting from a 128-bit plaintext $[B_0…B_{15}]$:

encipher $[B_0…B_7]$ with $K_1$, $[B_8…B_{15}]$ with $K_2$.
encipher $[B_4…B_{11}]$ with $K_3$, $[B_{12}…B_{15}]\mathbin\|[B_0…B_3]$ with $K_4$.
encipher $[B_0…B_7]$ with $K_5$, $[B_8…B_{15}]$ with $K_6$.