"I want you to say".

"I wnat you to do".

Thanks.

Is mian liom thú ... a rá
Is mian liom thú... a dhéanamh

or

Is mian liom go ndeire tú...
Is mian liom go ndéana tú...

I'd say

"Abair X, le do thoil"
"Déan Y, le do thoil"

A lughaidh, cén bunús gramadaí atá le seo (atá im chluas; baint éigin acu leis an Modh Conníollach)

Is mian liom go ndéanfá
Is mian liom go ndéarfá

Thig leat feidhm a bhaint as an mhodh choinníollach anseo nó as an mhodh fhoshuiteach. Ní hionann ciall an dá mhodh sin go díreach, tá níos mó méine ins an mhodh fhoshuiteach agus níos mó amhrais ins an mhodh choinníollach. Sin a’ méid.

An rud a scríobh tú leis an mhodh ordaitheach níl a’ chiall chéarna leis: "say X, please" "do Y, please". Ní hionann sin agus ceist Dhavid...

Is eol dom sin.
Ach braithim go mbeadh sin níos nadúrtha sa Ghaeilge. Feictear dhom go nusáidtear an Modh Ordaitheach níos minice sa Ghaeilge - ach má deir duine leat i mBéarla, "I want you to do", ordú is minice atá i gceist.
"I would like" a fhreagródh don Modh Fhoshuiteach (feictear domhsa).

David, to summarise the discussion between Lughaidh and myself;

You could use either the Modh Ordaitheach (Imperative)

Abair X, le do thoil

Déan Y, le do thoil

Say/do X/Y please

or the Modh Conníollach (Subjunctive)

Is mian liom go ndéarfá

Is mian liom go ndéanfá

or Modh Fhoshuiteach (used to express wishes, can't think of the english)

Is mian liom go ndeire tú...

Is mian liom go ndéana tú...

alternatively

Is mian liom thú ... a rá

Is mian liom thú... a dhéanamh

It depends on the setting/context which you would use.
I'd use the imperative if you expect it to happen - e.g a doctor saying to a patient "I want you to say Ah"

The order above is more or less the order of expectation that the person will say/do as you've asked.

thanks so very much! :-)

GRMMA

I want you to stick to the helm, though, as long as you can.

Is maith liom thú, ina dhiaidh sin, fanacht i mbun an halmadóra.

— Seosamh 'ac Grianna: Seideán Bruithne / Amy Foster
__________

I want you to draw my money and Jim's out of the bank; it's all in my name.

Ba mhaith liom tú mo chuid airgid féin agus cuid Shéamuis a tharraingt as an bhainc. Tá an t-iomlán in m'ainm-sa.
_____

Glad to hear it, but listen to me, my dear; I want you to know the truth.

Maise, is breagh liom a chluinstin, ach éist liom-sa, a chroidhe. Is maith liom tú an fhírinne a chluinstin.

— Domhnall 'ac Grianna: Gadaidheacht le Láimh Láidir
__________

I want you to take it home with you, and to mark off all the hardware sellers with their addresses.

Is é an rud a ba mhaith liom thú a dhéanamh an leabhar a thabhairt chun an bhaile leat agus ainmneacha agus seólta na ndaoine a dhíolas soithigh criadh a chur ar liosta leó féin.
_____

‘And now,’ said he, ‘I want you to make a list of the furniture shops, for they all sell crockery.’

‘Ba mhaith liom anois dá gcuirtheá na tighthe a mbíonn trosgán dá dhíol ionnta ar liosta eile,’ ar seisean, ‘nó bíonn soithigh criadh dá ndíol ionnta-san mar an gcéadna.’

— Proinnsias Ó Brógáin: Eachtraí Sherlock Holmes
__________

http://www.smo.uhi.ac.uk/~oduibhin/tobar/

Tá "is mian liom" níos laidre ná "is maith liom"

is maith liom = i like
ba mhaith liom = i would like
is mian liom = i want

Níl sé baileach chomh simplí sin, a Lughaidh.
Féach na samplaí a thug Peadar thuas.

Tá "is maith liom" sna samplaí úd níos gaire do "want" ná "like", sa mhéid is go bhfuil an cainteoir sách cinnte go ndéanfar rud air.

Yeah, but "is maith liom" meaning "i want" isn't common.