what are these smart switches? have you got a link to them of what they are and so on?
if you were to get a sparky to swap them over for you he would want to see the SDOC for the item, if it has a relevant SDOC and the sparky is happy he would complete the work then is required to supply a ESC for the work completed as its replacing a switch, a COC is not required as he wouldn't be relocating or adding anything to the circuit,
and as gregmcc mentioned you can pretty much do what you like in your own house electrically as long as its nothing to do with the switch board or metering, this is also outlined in ECP51 which you can google and have a read of,
Electricity Regulation 47
47. Home-owners' electrical wiring work
(1) For the purposes of section 110 of the Act, any person to whom
that section applies may do or assist in doing the following work on low
voltage electrical installations:
(a) Remove and replace any of the following kinds of fittings where
the work does not involve work on any switchboard:
(i) Switches:
(ii) Socket-outlets:
(iii) Permanent connection units:
(iv) Light fittings:
(v) Batten holders:
(vi) Cord grip lampholders:
(vii) Ceiling roses:
(viii) Flexible cords connected to any permanent connection
unit, ceiling rose, or cord grip lampholder:
(ix) Water heater switches:
(x) Thermostats:
(xi) Elements:
(b) Remove and replace fuse links:
(c) Connect and disconnect fixed wired appliances:
(d) Relocate existing switches, socket-outlets, and lighting outlets
that are supplied with electricity by tough-plastic-sheathed
cables:
(e) Install, extend, and alter subcircuits (including submains),
provided that–
(i) The person must not enter (whether personally, by holding
any material or equipment, or otherwise) any enclosure
where live active wires are likely to be present; and
(ii) The work is tested by a registered electrical inspector, in
accordance with NZS 3019, and the work is certified by
that inspector in accordance with regulation 39, before
being connected to a supply of electricity by such an
inspector.
(2) A person who carries out work pursuant to section 110 of the Act
must carry out the work in accordance with the requirements of ECP 51.
