I found an indication of how far to overlap tubes, from a LucasMilhaupt document on Brazing Joint Design. It gave a formula for how long the joint needed to be, based on the relative tensile strengths of the tubing material, and the shear strength of the filler material.

X = W*(D-W)*T / (C*L*D)

W = wall thickness of weaker member
D = diameter of lap area
T = Tensile strength of weaker memeber
L = shear strength of filler
C = "Joint integrety factor", suggested at 0.8

So, regular CP titanium is often listed at 345 MPa tensile, for T
W = 0.9 mm, D = 1.125*25.4 = 28.575 mm

L = 20 MPa is commonly listed for epoxy

X = W*(D-W)*T/(C*L*D)
X = 18.795 mm

So, the lug would need to be ~3/4" deep.

There are epoxies that advertise 60-80 MPa failure strength, but with yield strengths lower. (The Ti yield is also lower, more like 275 MPa). Using 3/2.5 Ti would take twice the overlap, to make the joint as strong as the tube, as it has > 600 Mpa tensile.

So, the good news for this approach is that we're not off by factors of 3-4. Deep lugs such as those meant for custom carving, and a good epoxy choice, might make this work out.