Regulator circuits in parallel - possible work around?

I've been using regulator circuits like the one attached for years without problem but would like to do the following:
(reducing a 12v DC to 9v DC - 1 amp regulator 7809 series)

I need 5 x 9v outputs from the same 12vDC supply. I would like to construct 5 (discrete) of the pictured supply.
The 12vDC input has the current capability required and each device plugged into the output would only need ½ of regulator chip's capacity. (I do not want five outputs regulated by one single circuit)

Q. Is it acceptable practice to place a blocking diode in series on the input side of each circuit (before the 1st cap) in order to isolate the following components to prevent every component becoming connected in parallel with each other?
Thanks for reading and look forward to your guidance.

Why not to use a booster transistor over the 7809 regulator to get 5A current capability for all 5 outputs to parallel loads?
The only possible advantage of five 7809 regulators is the 1A current limiting for each 9V load.
Using the series diode is possible but the voltage drop may affect the regulation of a 7809 as 3V more voltage input is required. One diode voltage drop is 0.7 V typ., so the input voltage should rather be 13 V instead of 12 V.
The more usual diode position to separate the loads is after the regulator but again the voltage drop will result in output voltage of 8.3 V instead of 9V.
For better results I would use five LM317T adjustable regulators for five 9V loads. No diodes are necessary and 1A limiting is met. For a larger current, LM350 offers up to 3A limiting.

Many thanks:
1. I don't want the devices connected to the output of one dropped supply.
2. Good.
3. Now not an issue maybe as I've pressed into service a 5amp 13.3v input supply.
4. Placing the diode after a regulator would surely only be appropriate if all devices were being supplied by one regulated 9v supply.

As mentioned, without some form of isolation (immediately after the 13.3v supply) I'm concerned the respective caps for each circuit would be in parallel with each other. But perhaps this is not an issue (at least with the electrolytics) as the values would be added?
I guess the main reason is to prevent the 7809s from being connected in parallel which, I understand after undertaking web searches, is a non-starter.

I note your comments regarding using five LM317Ts and have in fact noticed some very cheap small complete functioning modules on eBay utilising this chip but I would prefer to us components I have in my junk box first.

I would be grateful for your further thoughts on this project. Thank you jiripolivka.

I don't see a reason to isolate the voltage regulator inputs. Just connect them in parallel, forget about the diodes.

What's the purpose of the large capacitors before and after the voltage regulators?