Hello pupu.
What I have
- Nissin 466
Looks like the tilt feature could prove useful. A card could be attached to it to bounce and soften light some. Or it could be used remotely. In that case it could be bounced into an umbrella, a large white or foil card, or off a wall, or off a ceiling, etc. Keep in mind that if you bounce off of a wall or ceiling, the color of the wall or ceiling will be the color of the light that returns to your subject. Don't bounce off of a green wall with your primary light unless you want a green cast on your subject.
- on camera flash of 550D
I suppose there may be reflectors available which accomplish bounce with this. But keep in mind that bounce usually costs about two or more stops of light at the subject plane. The in-camera pop-up flash is not the brightest flash around. It might be better to think of your on camera flash as a trigger for more serious lights in your studio.
- an antique flash which my father purchased along with 'Hot shot' camera. No power setting option. It doesn't even have a name 
That old flash may prove useful in some capacity. I have several of those myself. However, be careful that its trigger voltage is low, not high. Some older flash units have trigger voltages in the hundreds of volts. Some modern cameras can tolerate less than ten volts at the flash trigger input terminals. It might be wise to check the voltage of the charged flash's trigger contacts with a voltmeter before attaching it to a modern camera body, or to its PC flash cord terminal. Your camera manual may have its flash trigger voltage limit defined within its specification page.
Plan I
Buy Yognou Rf triggers. From camera to 'antique via trigger and 'antique' to Nissin via optical slave. I don't know if the 'antique' will support the triggers or vice versa.
Another thought: There are some cheap optical triggers which will fire older flash units. I have one called a "peanut." It is essentially an SCR (silicon controlled rectifier), capacitor, resistor, and a photocell, all enclosed in a clear plastic blob. Looks similar to this one I found on B&H's site. $15.
Plan II
Use on camera pop-up flash but bounce it to trigger optical slave of Nissin.
You can probably use that technique to trigger both optically, as long as red-eye reduction pre-flash is off (or non-existent), with all the units.
So the question, is there any accessory which bounces/deflects the on camera flash, from the axis? 
Even if there isn't, you could make one with foil and tape. You just don't want very much of the harsh, direct light from your on-camera flash hitting the subject.
