Replacement capacitors should survive in any case, especially if machine racks up few hours of on-time after recapping. So don't worry about them. If worrying, worry about other components like the VDP that always tend to run hot.
Just to summarize your proposals, and not being able myself to solder: what can I do without changing any internal component?
Not much, really. The machine's logic/CPU/VDP etc will draw power (read: turn that power into heat), and no power supply is 100% efficient. So you will have losses (heat). But you can:
- Reduce those losses: more efficient power supply, NMOS -> CMOS Z80 etc.
- Move those losses elsewhere (external power supply).
- Reduce those losses' impact: ventilation holes / heatsinks / cooling fan.
Measures that make a big difference, will involve a soldering iron I think... And of course it may be good not to run your MSX in the peak heat of summer.
Personally I wouldn't ever let a cooling fan near my MSX. It kinda degrades the experience imho, and there's so many other measurers you can take. If you do: have a good look at the airflow you want, take the biggest 12V fan you can fit, and power it from the 5V (or even less by adding series resistor).
Ok guys thanks for your help. I'll post my experience and pictures when the baby arrives. I'll try not to stress it too much, maybe only using it with the bare recorder (no MFR). Cheers for now, and have yourself a happy Easter! 
Good luck orion70, hope you succeed.
I still don't use my HX-10 because of the heat issue. 
I opened the computer today. I have a different motherboard. I can not add photos from my computer. I checked where it is hot using my finger method. to replace 4 capacitors and installation of heat sinks.
this large radiator after 20 minutes was very hot. 77 degrees Celsius
I have to go shopping in part
I have a different motherboard.
You have the HX-10 Pal, I have the version NTSC. I think your board is same as below.
Components of the power supply must be about the same.
Small capacitor near the black regulator seems to annoy to put a heat sink. Pull a little the regulator to space it away from the capacitor.
The large heat sink heats up more if you add extension cartridges. I tried to put one a little bigger but it was not fit because of the case. So I looked for another one with more fins but I did not find one.
I replaced 5 capacitors
I've set up coolers. I did as you did. the transistor was moved away from the capacitor and the radiator was added. from an aluminum flat 25mm high and 2mm thick I made a cooler. mounted together with a thermally conductive paste.
the "finger" method looks better
written as always by google translator
