NRE/Lol

Graphemes
Unfortunately, there are a number of words which will still be different in different dialects.
 * e.g. bath; can be /bæθ/ or /bɑːθ/ and its plural can be /bæθs/, /bɑðz/ or /bæðz/.

These problems will just have to remain as the small number of words spelt differently in different dialects.

Rules
Some of these rules are optional and others are mandatory. Both rule types are in place to make communication as easy as possible, but the mandatory ones are seen as particularly important.

Common words
These common words are probably best written with the respellings below.

Invariable stems
Stems will remain the same when morphemes are added to them.
 * e.g. foutograf (photograph) + ï (y) → foutogräfï instead of *fotogräfï

This is to facilitate ease of identifying related words.

Following this rule, sliip (sleep) + d (ed) → sliipd (slept) [instead of *slepd] - still pronounced /slept/.

There are a number of things I don't like about this, but it also has a number of advantages. Thus, I include it as optional, so that others can make the difficult decision for me.

Past participles
All verbs take -en to make their past participle, rather than weak verbs taking -d. For instance, the past participle of lait (light) would be laiten instead of lit (or laitd if using invariable stems).
 * e.g. A poorly lit room would become A puurlï laiten ruum.

No reduced vowels
Reduced vowels may be seen to be adding a whole extra layer of complexity that is unnecessary. Thus, they can optionally be replaced as such: ê → a/e î → i ô → o û → u

Only one reduced vowel
Alternatively, all of the reduced vowels can be represented by the single grapheme ê.